A very interesting book by Sara Mednick. Available from Amazon
The book talks about how napping during the day to supplement night-time sleep is part of human nature. It makes specific reference to health and safety, including the role of fatigue in the Exxon Valdez accident.
A few snippets.
* In 1950's studies were done where subjects were kept in small flats without windows or clocks. After a short transitional phase people would sleep six to seven hours at a time that would represent night and roughly 12 hours later would return to bed for a shorter time. It is suggested that this is a natural sleep pattern.
* Before the light bulb was invented adults would typically get as much as 10 hours rest during the average weeknight. Today the average (in USA I presume) is 6.7 hours.
The book explains when to nap and for how long, but the basic message I take from it is napping can have great benefits, with small naps greatly reducing fatigue. I would not say I would follow detailed advice particularly, but it has encouraged me to take more naps whereas in the past I may have felt it a slightly silly thing to do. Also, it backs up advice I have given in the past for shift workers to have the opportunity to take short naps at works, especially when working nights.