Hey, I have been looking through some books and what not and constantly see the title: "The Trick That Fooled Houdini." But, I also so a video with Dai Vernon talking about an ACR that fooled Houdini.
So what really was the trick that fooled houdini???
The ACR???
Dissapearing Watch????
Or The Torn And Restored Newspaper???
Generally it's usually said to have been that one ACR with a double backer.
Tho as Vernon said "Houdini wasn't a magician, he made his career out of escaping things." so there could possibly be a ton of other things that fooled him. But most well known one was the ACR with the double backer.