Take a pack of cards with the corners at one end slightly cut off. Place
them all one way, and ask a person to draw a card; when he has done so,
while he is looking at it, reverse the pack, so that when he returns the
card to the pack the corner of it will project from the rest; let him
shuffle them; he will never observe the projecting card. Hold them
behind your back. You can feel the projecting card; draw it out, and
show it.