From the May 19th post "James Randi's own Shelton pool test" by John Cox at Wild About Harry:
On February 7, 1956, James The Amazing Randi recreated Houdini's famous Shelton pool test on the very site of Houdini's 1926 stunt. Randi said he wanted to prove that Houdini did not employ trickery; one really could remain alive in a space with limited oxygen using Houdini's principles.
Previously shared on Facebook May 19.