Secretly turning over the top card of the deck against the left leg is often credited to Jean Hugard, but it was earlier published by Alexander in The Sphinx, Vol. 32 No. 2, Apr. 1933, p. 58. Hugard later popularized the same method in his and Fred Braue's Royal Road to Card Magic, 1947, p. 177.
Hugard also published a related idea in Card Manipulations No. 2, 1933, p. 34. In this version, the card is transferred from the face of the deck to the back, with no reverse occurring.