And a scholar in England wrote that the time between the 'first sleep" and the 'second sleep' was the best time for serious study. - Delancey Place
"Something puzzled [Roger] Ekirch as he leafed through parchments ranging from property records to primers on how to spot a ghost. He kept noticing strange references to sleep. In the Canterbury Tales, for instance, one of the characters in 'The Squire's Tale' wakes up in the early morning following her 'first sleep' and then goes back to bed. A fifteenth-century medical book, meanwhile, advised readers to spend the 'first sleep' on the right side and after that to lie on their left. And a scholar in England wrote that the time between the 'first sleep" and the 'second sleep' was the best time for serious study...Numerous other studies have shown that splitting sleep into two roughly equal halves is something that our bodies will do if we give them a chance. In places of the world where there isn't artificial light - and all the things that go with it, like computers, movies, and bad reality TV shows - people still sleep this way.