Sources:

1) Anathalee 'bigann' Sandlin at allmanbrothersband.com (August 23, 2007, 12:14 PM):
"There is information in Johnny's bio I'm working on that talks about Duane when he first started playing slide. A trip to the Magic Mushroom to see Taj Mahal and Jesse Ed was the catalyst and the first song Duane ever played slide on in a band was the Taj Mahal version of Statesboro Blues with the Hour Glass."

2) Anathalee 'bigann' Sandlin at allmanbrothersband.com (September 22, 2011, 12:48 AM):
"Duane and the guys in the band went to the Magic Mushroom out in California to see Taj Mahal and after that night Duane started working on the slide. Gregg did bring him the Coricidin and Duane used the bottle when the medicine was gone. Johnny remembers being in his apartment and hearing Duane practicing down at his and at first it sounded horrible. Whenever anyone in the band called a song Duane was trying to play slide on they'd try to call something else before he reached into his bag to get the bottle. Then, it was like one day he figured it out and it all clicked for him."

3) Anathalee G. Sandlin: 'A Never-Ending Groove - Johnny Sandlin's Musical Odyssey', page 57 (Mercer University Press, 2012):
"About this time we went to a club called the Magic Mushroom near where we lived and saw Taj Mahal with Ry Cooder and Jesse Ed Davis. After that, Duane started learning to play slide and practicing in his apartment. He'd had a cold and bought a bottle of Coricidin, took the pills, and started using the bottle as a slide. I can remember going by his place and hearing him practice and wondering what on earth he was doing. When someone is learning to play slide, it's more than a little grating to people who have to listen to it - sort of like someone learning to play the violin. For a while it was driving me nuts, and I didn't understand why he wanted to do it"

4) Dave Kyle: 'Remembering Duane Allman' (Vintage Guitar Magazine, January 1997, Vol. 11 No. 4) https://www.duaneallman.info/rememberingduaneallman.htm :
"VG: Do you remember when you first saw Duane learning to play slide?
JS [Johnny Sandlin]: Yeah. He was in his apartment in L.A. with an old acoustic guitar. It didn’t sound very good al all back then when he first started. A lot of people don’t realize that before he learned to play slide, Duane was one of the top five players in the world. It seemed to me at the time that the slide was a detour in his playing. I’m not really proud of that lack of vision. Jesse Ed Davis was Duane’s very first influence. He got interested in slide after we’d seen Taj Mahal play sometime in ‘67. We loved that first Taj record, the whole band loved it - it was almost required listening. The Hourglass started playing Taj Mahal's version of "Statesboro Blues" shortly after that, and it was the first song I remember hearing Duane play slide on.
Later, he went back and listened to Elmore (James), Muddy (Waters) and other slide masters. Back then slide was a real strange thing. You didn’t see a young rock and roll band with a slide guitar player. Now you see it everywhere, but then I don’t even know if I realized what Jesse Ed was doing or how he was doing it. Duane didn’t invent slide, but he certainly popularized it and took it to new levels. It was just like a whole different instrument. Today you expect a lead guitar player to be able to at least play at it, but not then."

5) Galadrielle Allman: 'Please Be With Me: A Song For My Father, Duane Allman', page 102 (Spiegel & Grau, 2014):
"Duane was so happy to have Pete [Carr] around. He just had good energy and made Duane laugh. He walked around wide-eyed and amazed by everything he saw. During Pete’s first few weeks in L.A., they went to see Taj Mahal. They stood in the crowded club in front of Jesse Ed Davis and watched him play slide. He was a young Native American cat with a constant smile and black hair framing his face in a hip shag. His hands moved with a light, confident ease and he kept his eyes turned down toward his guitar like he was meditating. He pulled startling sounds so coolly out of his Fender with a bottleneck slide on his finger. Duane was mesmerized by it; he had never gotten such a good close look at the technique before. Taj sat on a stool wearing a wide-brimmed hat that shadowed his face and a red kerchief tied in a knot around his neck. His voice was so rich and warm, a pure blast of home, a shout rooted deep in the ground, real and raw. Taj blew his harp like a train swaying, and not a body in the room stood still. It struck Duane hard like a punch to his chest: This is it. This is the sound of no bullshit, of sweat and fire and home. This was church, a thunderclap, a call to arms. As soon as he got home, Duane sat down with a water glass and his guitar and tried to find those sounds. Then Gregg gave Duane a bottle of Coricidin cold medicine while Duane was laid up in bed sick as an old dog. Duane dumped out the pills and rested the small, perfectly formed bottle over his ring finger. He soaked the label off the bottle in the bathroom sink, put on Taj Mahal’s record, and got to work on "Statesboro Blues," learning Jesse Ed Davis’s licks note for note."

6) Alan Paul: 'One Way Out - The Inside History Of The Allman Brothers Band', pages 5-6 (St. Martin's Press, 2014):
"Around this time, most of the members of the Hour Glass went to see Taj Mahal at the Magic Mushroom, a club near their apartments.
Johnny Sandlin, longtime Allman friend and colleague; bassist in the Allman Joys and Hour Glass: Taj was great and so was his band, which included Jesse Ed Davis, playing slide guitar. Duane was knocked out by that slide playing and by "Statesboro Blues," which Taj had just cut on his first album. I went by Duane’s apartment a few days later and Duane was playing slide on "Statesboro Blues" and he was very excited about it.
"Statesboro Blues" was written and originally recorded by Blind Willie McTell in 1928, but it was a retake of Taj’s version that would become intimately linked with the Allman Brothers. From the start, Duane was using an empty bottle of Coricidian cold medicine as a slide. Gregg says the original slide came from a bottle he had given his brother when Duane was suffering from a bad cold."

7) Randy Poe: 'Skydog - The Duane Allman Story', pages 56-57 (Backbeat Books, 2006):
"We loved Taj Mahal," says Paul Hornsby. "We went out to see his band at a club that was called the Golden Bear, I believe." Pete Carr recalls the profound effect that night had on Duane: "We went to see Taj Mahal, and he had Jesse Ed Davis with him. They did 'Statesboro Blues,' and Davis played slide guitar on it. After hearing that, Duane started practicing slide all the time."
Jesse Edwin Davis III was a full-blooded Kiowa Indian. He would go on to work with such luminaries as Eric Clapton, John Lennon, Albert King, and Willie Nelson, among others. But in 1968, he was the lead guitarist in Taj Mahal’s band. "He made quite an impression on Duane," says Hornsby. "From the first time that we saw them, we picked up 'Statesboro Blues.' Taj was doing that, and from then on we claimed that song. That was the first song that Duane played slide on in the Hour Glass. Of course, now when you think of 'Statesboro Blues,' you think of the Allman Brothers' version, but Taj was doing it before them. We pretty much did the same arrangement as Taj." Everyone who was there at the time agrees that this was the moment of the Epiphany—the Magi had come bearing the gift, and Duane was there to receive it. On the down side, everyone also agrees that Duane's learning experience took it's toll on the assembled. "He drove us crazy," says Hornsby. "There’s nothing in the world worse than hearing somebody learn how to play slide guitar, unless it’s hearing somebody learn how to play the fiddle. I used to complain to Duane. Every time you'd see him, he was playing that damn slide—just driving you crazy."
Duane later recalled the torment he was inflicting on the other members of the Hour Glass: "I got me a [Coricidin] bottle and went in the house for about three weeks. I said, 'Hey man, we’ve got to learn the songs—the blues—to play onstage. I love this. This is a gas!' So we started doing it, and for a while it was everybody looking at me and thinking, 'Oh no! He’s getting ready to do it again!' Everybody just lowered their heads—start it off fast and get it over with. "But then I got a little better at it. . . ." It is a sentence that will go down as one of the great understatements of all time.

8) Randy Poe at allmanbrothersband.com (October 12, 2006, 11:37 PM):
"I've personally never heard anyone say (and I'm certain I didn't say in the book) that Duane wasn't familiar with the existence of the slide guitar prior to seeing Jesse Ed Davis. Duane would've been familiar not only with the blues guys of the past, but also with guys like (as you point out) Brian Jones of the Rolling Stones who played slide on some of the Stones's recordings.
I believe, in the book, I quoted Paul Hornsby talking about the Taj Mahal show. Others who were there that night were Pete Carr (who also says that's when Duane was inspired to take up slide playing) and Jeff Hanna of the Nitty Gritty Dirty Band.
I was with Willie Nelson and the NGDB for a week this summer up in Canada (just before the book was finished). The first night I was with them, we were backstage in some hockey rink somewhere in Nova Scotia. John McEuen told Jeff Hanna that I had been writing a book on Duane Allman. With no prompting from me, Jeff launched into the story about how he and the other guys in the NGDB had encouraged the Hour Glass guys to go with them to see Taj Mahal at the Golden Bear. Everyone went to the gig, Duane heard Taj and his band doing "Statesboro Blues," and from that experience, decided he had to learn to play slide. I wasn't one of the people there, but when three different people tell me they WERE there, and that this was the moment Duane decided to take up playing the slide, I've gotta believe Duane made it clear to the folks he was with that night that he had been inspired by what he'd heard.
There's a quote from Pete Carr in Guitar Player magazine in which he says, "I know *exactly* how Duane got into bottleneck. We were in L.A. and saw Taj Mahal playing in a club. Jesse Ed Davis was with him, and they did 'Statesboro Blues,' which was on one of their albums. Jesse played slide guitar and really turned Duane on -- bam!"
I did one of those audio channels for United Airlines a few years back. For that program, I asked Gregg why the ABB had chosen to cover "Statesboro Blues." He said he and the guys in the Hour Glass heard Taj Mahal doing it with Jesse Ed Davis playing slide, and they decided they had to start playing it too. And, when the ABB was formed, the song remained in the line-up.
Of course, there's a much easier way to get to the bottom of this. Give a listen to Taj Mahal's recording of "Statesboro Blues" on the Columbia album "Taj Mahal." If Duane wasn't inspired by Jesse Ed's slide performance, I'll eat my rock & roll shoes."

9) Randy Poe at allmanbrothersband.com (October 16, 2006, 04:32 AM):
"Both Paul Hornsby and Jeff Hanna told me they all (including Duane) went to see Taj Mahal play at the Golden Bear. Apparently he played there more than once during that era, so it'd be pretty difficult to pin down an exact date that Duane saw him and Jesse Ed Davis. Plus, "Statesboro Blues" had apparently been in Taj's repertoire for quite a while, since it was on those Rising Sons recordings from the mid-60s.
Pete Carr unintentionally added to the confusion when he said (in GP) [Guitar Player magazine] that the Golden Bear was in L.A. It wasn't until Jeff Hanna confirmed to me that the Golden Bear was in Huntington Beach that I realized Pete had been slightly off geographically. (Huntington Beach is about an hour from L.A.) I knew there was a Golden Bear in Huntington Beach, but when I read that Pete said it was in L.A., for a while I thought that maybe there were two different Golden Bears.
To add to the confusion, Taj Mahal also played the Whisky a Go Go during the Hour Glass era. So who's to say they didn't see Taj performing more than once, and in more than one venue?
When I was interviewing various people for the book, I was constantly trying to put myself in their shoes. 1968 was 38 years ago now. When I think back to monumental events in my life in 1968, I don't have a whole lot of clarity, so I can certainly understand if everyone's not remembering events from that time precisely the same way.
The thing that convinces me that the specific night Jesse Ed had such an affect on Duane was at the Golden Bear gig is because both Paul Hornsby and Jeff Hanna told me it was at the Golden Bear. I interviewed Paul two years ago (at which time he said, "I think the name of the club was the Golden Bear"), and I met Jeff Hanna this summer in Canada, at which time he told me, "We took Duane and the Hour Glass guys to see Taj Mahal at the Golden Bear in Huntington Beach." I don't think Paul Hornsby and Jeff Hanna have seen each other in over 30 years, so there's no way to chalk it up to an incredible coincidence or recent conversations between the two of them. Therefore, I took the two stories together to be about all the info I needed to conclude the story was accurate."

10) Randy Poe at allmanbrothersband.com (September 30, 2009, 05:34 PM):
"And if you're wondering where the ABB connection is in all of this, it's pretty safe to say there might have never been an ABB without the NGDB. John McEuen's brother discovered the act that became the Hour Glass while the NGDB were on tour in St. Louis. He also got the band their deal with Liberty Records. Duane, Gregg and the rest of the Hour Glass members actually lived with the Dirt Band when they first moved to L.A. And it was Jimmie Fadden who took Duane and the gang to the Golden Bear to see Taj Mahal. At that show, Duane saw/heard Jesse Ed Davis III playing slide guitar on Taj Mahal's version of "Statesboro Blues." And the rest, as they say, is history."

11) http://www.cavehollywood.com/duane-allmans-posthumous-career-retrospective-an-anthology-reissued-on-vinyl-via-mercuryume/ :
"California in the sixties was the center of the new musical movement formed by the psychedelic revolution, but they just didn't quite fit into the situation. However, Duane reputedly started playing slide guitar when he saw Taj Mahal perform at the Golden Bear in Huntington Beach."