Pythagorean Cup (Siphon Mug)

The "greedy cup" attributed to Pythagoras, as a mug: fill it a little and it holds; fill it past the line and it empties completely through a hidden siphon in the handle.

A fun puzzle about siphons and air pressure: why does it drain all the water, not only the extra?

Design by Fab3D Udesc on Printables, shared under CC BY 4.0. The files and photos are the designer's, unchanged.

1. Print version 2: it starts draining at about two-thirds full.
2. Use it over a tray or sink. Not for drinks: FDM prints are not food safe.
3. Students predict what will happen, test it, then cut a drawing in half to explain the siphon.