Markandeya Purana 34.82

34.82

vidharmiṇo 'hni pūrvākhye sandhyākāle ca ṣaṇḍakāḥ /
kṣurakarmaṇi vānte ca strīsambhoge ca putraka //

“A woman, during menstruation, should be avoided by all the castes for four nights. He should avoid just the fifth night of the moon in order to avoid the birth of females: then let him approach his wife on the sixth night, that night is the best among the even nights, my son. Sons are begotten on the even nights, daughters on the odd nights: therefore a wise man who wishes for a son should always cohabit with his wife on the even nights. Lawless men cohabit with their wives in the morning, and eunuchs at evening.

“After shaving, and vomiting and sexual intercourse, my son, the wise man should resort to the place where bodies are burnt[12] and should bathe, keeping his clothes on.