The medium Henry Slade was caught in fraud many times throughout his career. In a séance in 1876 in London Ray Lankester and Bryan Donkin snatched his slate before the "spirit" message was supposed to be written, and found the writing already there. Slade also played an accordion with one hand under the table and claimed spirits would play it. The magician Chung Ling Soo revealed how Slade had performed the trick.
In 1880 the American stage mentalist Washington Irving Bishop published a book revealing how mediums would use secret codes as the trick for their clairvoyant readings. The Seybert Commission was a group of faculty at the University of Pennsylvania who in 1884–1887 exposed fraudulent mediums such as Pierre L. O. A. Keeler and Henry Slade. The Fox sisters confessed to fraud in 1888. Margaret Fox revealed that she and her sister had produced the "spirit" rappings by cracking their toe joints.