Pythagorean Cup: Practical Joke Chalice
http://99percentinvisible.org/article/pythagorean-cup-practical-joke-chalice-overflows-ancient-greek-humor/

“When the cup is filled too high […] the entire contents of the cup begin to drain […] If filled to just below that point, however, a user can drink from the vessel normally.”

“As the (possibly apocryphal) story goes: Pythagoras designed the cup so that his students […] balance their consumption.” https://mastodon.social/media/5ioXpkyh6uILzJzp3I8