I used to be heavily into magic and Houdini, who was friends with Doyle for a time. Despite the supernatural never appearing in a Sherlock Holmes story, Doyle believed in the supernatural. I think this lead to a falling out between him and Houdini, who regularly debunked psychics and other such claims.

There is a short treatment on the Cottingley Fairies in James Randi's book Flim Flam.

People believed some odd things in the 1970s as well. Take Kirlian photography. Also, there was a technique that I cannot remember the name, but involved concealing a small tube with a bit of negative in ones hand, and pointing a camera (usually a Polaroid) toward ones forehead to produce an amazing "supernatural" photo.