Kamasutra 5.6.28

5.6.28

parasparasya kāryāṇi jñātvā cāntaḥpurālayāḥ/
ekakāryās tataḥ kuryuḥ śeṣāṇām api bhedanam//
dūṣayitvā tato 'nyonyam ekakāryārpaṇe sthiraḥ/
abhedyatāṃ gataḥ sadyo yatheṣṭaṃ phalam aśnute//

The entrance of young men into harems, and their exit from them, generally take place when things are being brought into the palace, or when things are being taken out of it, or when drinking festivals are going on, or when the female attendants are in a hurry, or when the residence of some of the royal ladies is being changed, or when the King's wives go to gardens, or to fairs, or when they enter the palace on their return from them, or lastly, when the King is absent on a long pilgrimage. The women of the royal harem know each other's secrets, and having but one object to attain, they give assistance to each other. A young man, who enjoys all of them, and who is common to them all, can continue enjoying his union with them so long as it is kept quiet, and is not known abroad.