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.<p><a href="http://www.kleinbottle.com/Tantalus.html" rel="nofollow">http://www.kleinbottle.com/Tantalus.html</a>
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.
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?
Here's a neat 4 min video demonstrating how the cup works & how to "beat" it with mercury: <a href="https://www.youtube.com/watch?v=ISfIT3B4y6E" rel="nofollow">https://www.youtube.com/watch?v=ISfIT3B4y6E</a>
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.<p>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.