Maxello Magic

Performer shows two plastic cups or vases. Four coins are tipped out of each vase. These are dropped back, four in each vase. The performer mimes removing one coin invisibly from one vase and tossing it into the other. When the vases are tipped over again, three coins emerge from one vase, and five coins from the other. One coin has apparently traveled from one vase to the other. The coins are replaced and this is repeated, with one coin repeatedly vanishing from one vase and re-appearing in the other, till all eight coins have gathered in the same vase.

Once you know the basic principle, you can modify this basic routine for six coins or four, as you wish.