I've been fascinated over the last couple of days by Sean Coughlan's book The Sleepyhead's Bedside Companion. Leaving aside the rather twee title I found this well worth reading. There is no index though the contents list is comprehensive. It is not a scholarly book and there is no list of sources but there is enough information given with each subject to allow you to identify its source if you wished.
I was intrigued to learn that the basic design of beds has not really changed since human beings first started looking for somewhere to curl up. I was not aware that sleep deprivation can be more dangerous and more quickly fatal than starvation. Pyjamas come from an Indian word and at one time sleep was not considered an indication of idleness as it is today.
This is a book for dipping into - perhaps if you are unable to sleep. Though insomnia, if it is real rather than simply a fashionable pose, can kill you. If you were that way inclined you could start worrying about the effects of your insomnia and make the problem worse. Apparently human beings right up until the nineteenth century didn't confine sleep to one block of time during the day.
They might sleep until about midnight then wake up for an hour or so to talk, eat, drink or read or write and then go back to sleep. The human system is far better suited to this regime which probably accounts for the fact that if I stay up until midnight - rare these day - I seem to wake up rather than get more sleepy.