Houdini performed at least three variations on a buried alive stunt during his career. The first was near Santa Ana, California in 1915, and it almost cost Houdini his life. Houdini was buried, without a casket, in a pit of earth six feet deep. He became exhausted and panicked while trying to dig his way to the surface and called for help. When his hand finally broke the surface, he fell unconscious and had to be pulled from the grave by his assistants. Houdini wrote in his diary that the escape was "very dangerous" and that "the weight of the earth is killing."  Houdini's second variation on buried alive was an endurance test designed to expose mystical Egyptian performer Rahman Bey, who had claimed to use supernatural powers to remain in a sealed casket for an hour. Houdini bettered Bey on August 5, 1926, by remaining in a sealed casket, or coffin, submerged in the swimming pool of New York's Hotel Shelton for one and a half hours. Houdini claimed he did not use any trickery or supernatural powers to accomplish this feat, just controlled breathing. He repeated the feat at the YMCA in Worcester, Massachusetts on September 28, 1926, this time remaining sealed for one hour and eleven minutes.  Houdini's final buried alive was an elaborate stage escape that featured in his full evening show. Houdini would escape after being strapped in a straitjacket, sealed in a casket, and then buried in a large tank filled with sand. While posters advertising the escape exist (playing off the Bey challenge by boasting "Egyptian Fakirs Outdone!"), it is unclear whether Houdini ever performed buried alive on stage. The stunt was to be the feature escape of his 1927 season, but Houdini died on October 31, 1926. The bronze casket Houdini created for buried alive was used to transport Houdini's body from Detroit to New York following his death on Halloween.

Answer this question "What was the second variation?" by extracting the answer from the text above.
Houdini's second variation on buried alive was an endurance test designed to expose mystical Egyptian performer Rahman Bey,