Robert H. Gysel (1880-1938) was a professional spirit medium who turned professional magician in 1901. Finding more success as a debunker of fake spirit mediums, he was also an accomplished lock-picker and escape artist. Of course, he and Houdini had a lot in common. By 1920, Gysel was the trusted secret assistant to Harry Houdini, helping to infiltrate and expose the many spirit medium circles in operation at the time.
Astonishingly, "true skeptic" Gysel began experiencing strange phenomena himself in October 1926. Gysel predicted Harry Houdini's death in a letter written to friend and fellow magician Fulton Oursler on October 25, 1926. He reported that the night before, Houdini's piture had fallen off the wall, smashing to bits. "I know now Houdini will die", he wrote. And on October 31, just 6 days later, Houdini was dead.
This envelope, dated 1925, was sent from Toledo, Ohio, Gysel's home town.