According to the magician John Booth the stage mentalist David Devant managed to fool a number of people into believing he had genuine psychic ability who did not realize that his feats were magic tricks. At St. George's Hall, London he performed a fake "clairvoyant" act where he would read a message sealed inside an envelope. The spiritualist Oliver Lodge who was present in the audience was duped by the trick and claimed that Devant had used psychic powers. In 1936 Devant in his book Secrets of My Magic revealed the trick method he had used.[162]
The psychical researchers Eric Dingwall and Harry Price re-published an anonymous work written by a former medium entitled Revelations of a Spirit Medium (1922) which exposed the tricks of mediumship and the fraudulent methods of producing "spirit hands".[135] Originally all the copies of the book were bought up by spiritualists and deliberately destroyed.[136] In 1923, the magician Carlos María de Heredia revealed how fake spirit hands could be made by using a rubber glove, paraffin and a jar of cold water.[137]
^ "Glossary of Key Words Frequently Used in Parapsychology" Archived 2010-12-24 at the Wayback Machine, Parapsychological Association website. "Materialization: A phenomenon of physical mediumship in which living entities or inanimate objects are caused to take form, sometimes from ectoplasm." Retrieved January 24, 2006 "Medium – Definition". Retrieved 23 March 2007.