I blame it on alcohol. If I drink I’m always up for a few hours in the middle of the night. And I’m quite sure they were doing a lot of that back in that time.
Of course actual blood alcohol takes longer to go down than that but no matter how much I had, I'd invariably feel significantly more sober after the initial sleep than if I just stayed awake and stopped drinking.
Given that alcoholic drinks (especially various concoctions we'd hardly recognize as "beer" today) were fairly widespread especially when pure water was not always potable, I wouldn't be surprised if this didn't at least factor in for some of the reports. Then again this doesn't explain the observation of polyphasic sleep developing under experimental conditions.
Technically, they were all drinking alcohol because water was unsafe. However, beer at least had half the alcohol content that it has today and the wine was strongly watered. For women and children they even added water to the beer.
Googled it once. The information should still be available.
almost no one here is willing to admit, in the heat of a discussion, that they don't know everything about the topic at hand, and it is maddening.