^ Paul Kurtz. (1985). A Skeptic's Handbook of Parapsychology. Prometheus Books. p. 29. ISBN 978-0-87975-300-9 "Florence Cook was caught cheating not only before her séances with Crookes but also afterward. Furthermore, she learned her trade from the mediums Frank Herne and Charles Williams, who were notorious for their cheating." Also see M. Lamar Keene. (1997). The Psychic Mafia. Prometheus Books. p. 64. ISBN 978-1-57392-161-9 "The most famous of materialization mediums, Florence Cook – though she managed to convince a scientist, Sir William Crookes, that she was genuine – was repeatedly exposed in fraud. Florence had been trained in the arts of the séance by Frank Herne, a well-known physical medium whose materializations were grabbed on more than one occasion and found to be the medium himself."
Senses used by mental mediums are sometimes defined differently from in other paranormal fields. A medium is said to have psychic abilities but not all psychics function as mediums. The term clairvoyance, for instance, may include seeing spirit and visions instilled by the spirit world. The Parapsychological Association defines "clairvoyance" as information derived directly from an external physical source.