I found this extract in
a BBC story on the myth of the consecutive 8-hour sleep need:-
A doctor's manual from 16th Century France even advised couples that the best time to conceive was not at the end of a long day's labour but "after the first sleep", when "they have more enjoyment" and "do it better".
Well, we knew that in Judaism.
Tractate Berachot 3
For it has been taught: R. Eliezer says: The night has three watches...In the first watch, the ass brays; in the second, the dogs bark; in the third, the child sucks from the breast of his mother, and the woman talks with her husband.
Moreover, in this doctorate of Anat Kutner,
The Night in the Late Middle Ages in Ashkenaz (in Hebrew), the 7th chapter describes in great detail sexual customs. From page 234 on there are discussions based on Halachic sources.
On page 250, Rav Aaron of Navorna is quoted in his Orchot Chayyim, p. 75, that the middle of the third watches of the night is conducive to sexual relations. This follows
the Rambam, Deot 5:4
Although a man's wife is permitted to him at all times, it is fitting that a wise man behave with holiness. He should not frequent his wife like a rooster. Rather, [he should limit his relations to once a week] from Sabbath evening to Sabbath evening, if he has the physical stamina.
When he speaks with her, he should not do so at the beginning of the night, when he is sated and his belly [is] full, nor at the end of the night, when he is hungry; rather, in the middle of the night, when his food has been digested.
He should not be excessively lightheaded, nor should he talk obscene nonsense even in intimate conversation with his wife. Behold, the prophet has stated (Amos 4:13): "And He repeats to a man what he has spoken." [On this verse,] our Sages commented: A person will have to account for even the light conversation that he has with his wife.
[At the time of relations,] they should not be drunk, nor lackadaisical, nor tense - [neither both of them,] or [even] one of them. She should not be asleep, nor should the man take her by force, against her will. Rather, [the relations should take place] amidst their mutual consent and joy. He should converse and dally with her somewhat, so that she be relaxed. He should be intimate [with her] modestly and not boldly, and withdraw [from her] immediately.
This is repeated, curtly, at
Issurei Bi'ah 21:10
It is the course of holy conduct to engage in relations in the middle of the night (In Hilchot Deot 5:4, the Rambam gives a rationale that at this time a person's food will have been digested and yet, he will not be overly hungry. The commentaries to Nedarim 20b explain that in this manner, the man and his wife will have forgotten all their daytime concerns and will be able to focus their attention on each other and the holiness of the experience).
The
Shulchan Aruch Orach Hayyim 240:8 adds that it is best in the middle of the night so that he should not hear any other voice and come to impure thoughts.
So, hundreds of years before the 16th century, we knew what's best.
^