Dr. Elliott first established the principle in Goldston's Annual of Magic, 1909/10, p. 27, using a top card with one corner torn off. Ellis Stanyon published the idea with a half-moon cutout at the front of the card in Magic, April 1913, p. 54. Vernon refined it by using just a punched hole in the top card, which appeared in his Ten Card Problems, 1932, p. 12.