One of the most fascinating, and somewhat sad, things Sir Conan Doyle, the author of the Sherlock Holmes detective series, accepted Theosophy completely right down to the existence of fairies. One of his not so memorable books was entitled The Coming of the Fairies. In it he tried to prove the existence of those wee critters by using the most ridiculous and obviously fake photographs. A supreme irony that he was the author of a character that was a super logical detective.
Doyle was haunted, not by demons but by many of his dead relatives who died a premature death during his lifetime. He took comfort with Theosophy's promise that one can communicate with the dead.
Below is one of the photographs that he took seriously in his book.