"The painter Salvador Dali used to employ the following trick to have the best nap ever:

Hold a coffee spoon (or something else—use your imagination) in your hand.

Sit and relax on a comfy couch or chair with your arm hanging.

When you go into deep sleep (after about 20-30 minutes) your hand will relax and release the spoon, and the sound of the spoon falling will wake you up.

That is the perfect timing for the best nap ever."

http://www.lifehacker.com.au/2009/08/from-the-tips-box-coffe...