Under the Quora question "What is something useful I can learn right now in 10 minutes that would be useful for the rest of my life?" Swami Nathan posted a sleep hack called Polyphasic Sleep:

You may know that sleep is divided into five stages. Polyphasic sleep concentrates on the fifth and most important stage of sleep, rapid eye movement (REM.) This is the most beneficial stage of sleep; it is when the brain is most active and is when dreaming occurs. REM is the only stage of sleep that is actually required to survive and function normally. The interesting part of all this is that you only spend 1 to 2 hours in this stage of sleep every night. The other 6 or so hours spent asleep every night are seemingly wasted.

Polyphasic sleep cycles basically cut out the other useless phases, giving you an additional 4 to 6 hours of time awake.

I enjoy my sleep, but perhaps I could get the same pleasure with less time. Here's one polyphasic sleep cycle pattern:

The Siesta

This sleep cycle is actually pretty common around the world in warmer countries such as Latin America, where the temperature is so hot during the middle of the day that people retire to take a short nap after lunch. It involves 6 hours of core sleep and one short 20-30 minute nap. You will find in these countries that most shops close during the early afternoon, as everyone is ‘busy’ taking their siestas!

I'm surprised I don't see any answers from Tim Ferriss in that Quora thread.

Hmmm, it's early afternoon here in San Francisco. I'm going to take a 20 minute siesta.