Cliff Stoll has a page about this. He calls it a Cup of Tantalus and it's part of his Klein Bottle collection. Makes for a fun gift for geeks.

http://www.kleinbottle.com/Tantalus.html

In respect of the greeks, this is one cheap souvenir that can actually provide timeless merriment. I have a few made of burnt clay that are souvenirs from decades ago and still there are new people who can delightfully be educated on the principles of these wonderfull devices.

Wouldn't it actually be very annoying to have to mop and/or clean things every time?

Some houses are equipped with sinks, bathubs, etc :)

Ah yes, the old "Here's your completely ordinary cup of wine. Please drink it over the sink for no particular reason" gag. Gets them every time! :)

Just call it libation without inclination.

With respect to "drinking normally" when the cup is filled below the siphoning point: if you drink by tipping the cup towards the drain pipe, wouldn't that engage the siphon?

The drain pipe is as close to the center as possible. When you tilt a cylinder half full of water, the point at the center remains at the same height. Considering the cups are slightly wider at the top than the bottom, it can hold more liquid when tilted, so the height at the center would be a bit lower.

Here's a neat 4 min video demonstrating how the cup works & how to "beat" it with mercury: https://www.youtube.com/watch?v=ISfIT3B4y6E

Neat. It's like a tiny toilet.

Self flushing urinals used to work this way. The tank above the urinal was filled at a constant rate, and would discharge when the level ran over the top of the siphon.

I remember this cup. I also remember thinking Those both greedy and smart could have simply plugged the hole with their finger and all is good.

Pythagoras should have given his students smaller normal cups because, if we go Machiavellian for a moment, people are unscrupulous and will plug the hole, therefore a smaller cup will be more effective. And limited servings.

You can make this harder by providing multiple small holes all over the bottom of the cup.

This is how toilets work.

Anywhere to buy one cheaply?

3D print one?

3D printing stuff that's foodsafe is nontrivial. You not only need a material that is not directly harmful (in temperatures it will be used in), but also most 3d printed surfaces will not be smooth. This makes them very hard to properly clean (especially the parts of such a cup that wouldn't be reachable), which causes biological problems (bacteria and mold growing there).

Whatever material such a cup was made out of, I'd've wanted to be able to dismantle it for cleaning, which lessens the advantage of 3d printing over more traditional fabrication techniques.

Also like Soxhlet extractors. That is the coolest chemistry glassware.

I'd encourage anyone to read up on Pythagoras. He was a really weird guy who held some inane beliefs and superstitions. Also a cult leader.

I don't think we can know what he really believed or if he existed at all. He's a semi-mythical figure and there are no contemporary accounts of him.