Nail Writing is the act of using a finger-tip device with pencil-lead or chalk, typically wedged under the fingernail, to permit secret writing during a Slate Writing presentation. Also known as a Swami Gimmick or boon.
This technique originated among mediums of the late 1800s. "Dr" Henry Slade was caught using one by John W. Truesdell in 1872.
- Spirit Slate Writing and Kindred Phenomena by William E. Robinson (Chung Ling Soo) (1898)