A story, perhaps apocryphal, about Thomas Edison. He would hold ball bearings in his hand as he fell asleep, and the noise of them falling to the floor would wake him immediately as he went to sleep, thus generating the shortest possible power nap.

There's a decent chance that story is actually lifted wholesale from a similar one told about Dali, except it was a spoon instead of ball bearings. I suppose it's the best you can do after melting your alarm clock.