Juggling three
balls (or other juggling equipment) in one hand. This is one of those tricks you learn at around the same time as you are
learning five balls, and is needed before you attempt the
six ball fountain.
In the two in one hand pattern, there are three possible patterns for the balls to follow - side by side, inside to out, and ouside to in. When juggling three in one hand, however, there are two more; the cascade and the reverse cascade. In both cases, the balls move in a figure-of-eight pattern, and your hand throws first on the left, then on the right.
The reverse cascade pattern is generally considered the easiest, since all the balls come down in the middle. The cascade pattern is the next easiest, and many people use this one, but the one you will have to master eventually is the inside-to-out pattern, since it is needed for the six ball fountain.
Good luck, you crazy person!