These sources accompany the (mini) tenth episode of the Joy of Text podcast.
Hippocrates, On the Generating Seed and the Nature of the Child 4-5
(4) In the case of women, it is my contention that when during intercourse the vagina is rubbed and the womb is disturbed, an irritation is set up in the womb which produces pleasure and heat in the rest of the body. A woman also releases something from her body, sometimes into the womb, which then becomes moist, and sometimes externally as well, if the womb is open wider than normal. Once intercourse has begun, she experiences pleasure throughout the whole time, until the man ejaculates. If her desire for intercourse is excited, she emits before the man, and for the remainder of the time she does not feel pleasure to the same extent; but if she is not in a state of excitement, then her pleasure terminates along with that of the man…. The pleasure experienced by the woman during intercourse is considerably less than the man’s, although it lasts longer. The reason that the man feels more pleasure is that the secretion from the bodily fluid in his case occurs suddenly, and as the result of a more violent disturbance than in the woman’s case.
Another point about women: if they have intercourse with men their health is better than if they do not…
(5) When a woman has intercourse, if she is not going to conceive, then it is her practice to expel the sperm produced by both partners whenever she wishes to do so. If however she is going to conceive, the sperm is not expelled, but remains in the womb. For when the womb has received the sperm it closes up and retains it, because the moisture causes the womb’s orifice to contract. Then both what is provided by the man and what is provided by the woman is mixed together. If the woman is experienced in matters of childbirth, and takes note when the sperm is retained, she will know the precise day on which she has conceived.
בעלי הנפש שער הקדושה
ומי שאומד את עצמו שיוכל לעשות כך ולא תכנס עליו מחשבה אחרת, והוא משהא עצמו כדי שתהנה האשה מן המעשה ותזריע תחילה, מתכוין לעשות מצוה ועושה אותה והקב”ה נותן לו שכרו בבנים זכרים
Raavad, Ba’alei Hanefesh, Gate of Holiness
Someone who assesses himself that he can act thusly (“delaying on the womb”) and no foreign thought will enter his mind, and he “delays on the womb” so that his wife derives pleasure from the act and gives forth seed first – such a person is intending to do a mitzvah and he is doing a mitzvah, and God will give him his reward with male children.