This uses sponge rhomboids (sort of demented cubes) with which you do a really entertaining routine -- the sponges vanish, transpose, and so forth, in the standard sponge ball routine. Now comes the big finish -- you ask the spectator how many sponges are in your hand. No matter what they answer, the true number is four... and you open your fist and there is a giant sponge in the shape of the number 4. A surprising climax to a great routine.