Also known as “table tipping.” A way spiritualists believed they could communicate with the deceased. Sitters would lightly place their hands on a central table and in a few moments the table would move, rotate, rise up on one leg, or even completely levitate. By rising up on a leg and coming down with a knock, a code could be set up with the deceased (1 for A, 2 for B, etc.). Unfortunately, this was very time consuming and other systems, especially the Ouija, developed.
Skeptics determined that the actual cause of the table’s movements (excluding outright fraud) were unconscious muscular actions also known as ideomotor responses. What they couldn’t describe, however, is where those messages came from, especially when the participants couldn’t have known the transmitted information.