This was probably the most challenging episode to make ever. It goes into much detail about an alternate sleeping schedule called Polyphasic sleep. Human sleeping patterns used to be very different when compared to modern times. Did you know the monophasic 8-hour sleeping schedule is actually not natural to us? Well, there's much more interesting things to learn about sleep in this episode.

Here are some links to the books referenced in the show as well as puredoxyk.com

At Days Close Nights of Life Past

The Biology of Belief

Ubersleep