The man sitting across the table from you is known for trickery. He is a stage magician. You know he employs trickery, so he tells you he is going to do a card trick in which he can't possibly manipulate the cards. In this trick, you will do all of the card handling. He won't touch the cards at all.
He instructs you to cut the deck into four piles. You do so. He then tells you that you are going to randomize the order of the cards by shuffling them around and moving cards from one pile to another. Pointing to a pile of cards, he instructs you to take the top three cards and place them at the bottom of that pile. Then, take the next three cards and place them, one each, on top of the three piles remaining on the table. You repeat the procedure with all four piles of cards. The cards should now be very well mixed.
The man then begins his patter in earnest. He asks you to confirm the fact that he has not touched the cards. You agree. In no way could he have manipulated how you would cut the cards or handle them. Again, you agree. With a smile, he asks you to turn over the top card from each pile. You are amazed. The four aces sit at the top of each of the four piles of cards. For a moment, your mind might actually entertain the possibility that real magic has been performed, though you "know" you've been duped.