Arthur Conan Doyle became interested in Spiritualism as early as 1886, inspired by the writing of the US High Courts Judge John Worth Edmonds, and confessing his belief in the supernatural in various publications, including The Coming of the Fairies, "a collection of facts" about the Cottingley Fairies, published a year after the start of an odd friendship. In 1920, Doyle received the book The Unmasking of Robert-Houdin from none other than Harry Houdini, the renowned magician turned resolute skeptic, yet the two became friends, discussing spiritualism in terms of faith and frauds, respectively. [more inside]
Ehrich Weisz may not have had much formal education, but he grew up to be Harry Houdini, self-educated stunt performer, escape artist, and owner of "one of the largest libraries in the world on psychic phenomena, Spiritualism, magic, witchcraft, demonology, evil spirits, etc., some of the material going back as far as 1489." Houdini bequeathed much of his collection to the Library of Congress, which received 3,988 volumes from his collection in 1927, including a number of magic books inscribed or annotated by well-known magicians. Archive.org has more of the Harry Houdini Collection online. He also put a great deal of research into his tricks, as seen in his letter to Dr. W. J. McConnell, a physiologist at the U.S. Bureau of Mines, written up after Houdini's watery grave stunt in 1926.