Teller reveals the tricks of perception that magicians have mastered. Among them:
[In 1907 David P. Abbott] used to make a golden ball float around his parlor. After the show, Abbott would absent-mindedly leave the ball on a bookshelf while he went to the kitchen for refreshments. Guests would sneak over, heft the ball and find it was much heavier than a thread could support. So they were mystified. But the ball the audience had seen floating weighed only five ounces. The one on the bookshelf was a heavy duplicate, left out to entice the curious. When a magician lets you notice something on your own, his lie becomes impenetrable.
(Card trick via The Next Web and the revealed "magic" here.)
The Dish 