Steel Ball and Tube by E-Z Magic
A brass tube and solid steel ball are offered for examination. The ball is LARGER than the diameter of the tube, but the magician causes the ball to sink INTO the tube and rise again. Of course, should someone else try, they find it impossible as the ball remains on top of the tube. A splendid pocket trick!
Be sure to check out a great variation on this classic trick called Molten Ball!