I first stumbled upon this concept a year or so ago in a Steve Mould science video, linked here. It explained the physics behind the amazing hydrodynamic mechanism called the Pythagorean siphon, also known as a greedy cup siphon. I have been fascinated with this idea for a while, so I designed and 3d printed a functional greedy cup. It works like a regular cup until the water level reaches the top of the cylinder in the middle, which sets off the siphon mechanism and causes the water to drain out the bottom. This design was used in history to punish greedy drinkers by draining their cups when they poured too much, but is also a really fun party trick and a great demonstration of the capabilities of 3d printing.