Tantalus Cup
by GSC International

The Tantalus Cup is known as a Pythagorean Cup, Pythagoras Cup or Greedy Cup, and can be used as either a physics demonstration or a practical joke. An inverted glass U-tube sits in the middle of the glass, extending through the stem and into the open bottom. A rubber stopper forms a seal between the tube and glass, allowing it to be filled without leaking.

At first, the water is forced into the tube so that equilibrium in the cup is maintained. Once the equilibrium point has been passed, the tube starts working as a siphon, draining the cup until such time as the open end of the U-tube inside the cup is finally exposed to the air.

While Pythagoras did not invent the syphon, he is the one that has been credited with the creation of the Greedy Cup. The cup allows the one drinking from it to fill wine to a certain level. If they only fill the cup to that point, or below, they are free to drink in peace. If they are feeling particularly gluttonous and fill beyond that point, almost the entire contents of the cup are emptied out of the bottom, typically on the lap of the glutton.

Not to be confused with the “dribble cup”, which has tiny holes hidden in the designwork on the drinking vessel.