Green’s Dictionary of Slang

in cards, cheating by secreting a number of cards on one’s knee, or wedged between a knee and the underside of the table. These cards can be brought into the hand, swapping them for those one has been dealt, as and when required.

1803		Sporting Mag. XXI 326/2: Weaving — Is securing one or more cards upon the knee, under the table played at.
1864, 1867, 1870		Hotten Sl. Dict. 267: Weaving a notorious card-sharping trick, done by keeping certain cards on the knee, or between the knee and the under side of the table, and using them when required by changing them for the cards held in the hand.
1873		Sl. Dict.