The forgotten medieval habit of 'two sleeps'
For millennia, people slept in two shifts – once in the evening, and once in the morning. But why? And how did the habit disappear?
https://www.bbc.com/future/article/20220107-the-lost-medieval-habit-of-biphasic-sleep?
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... about the "watch(ing?) hour", and how people used to sleep in two shifts. I had thought "The Watching Hour" was the title of the book being discussed with its author, but I could never find a book by that title. Finally, I did come across the book mentioned in the BBC article, which is probably the same one, but haven't read it yet (it's quite long 
).
My new word for the day is "cathemeral", meaning awake during both night and day. I guess it is the complement of "crepuscular", meaning active in the twilight hours, as cats are -- suggesting that cats and humans have naturally opposite circadian cycles. 
Closing my eyes, will see for how long.
