Kamasutra 2.2.31

2.2.31

śāstrāṇāṃ viṣayas tāvad yāvan mandarasā narāḥ/
raticakre pravṛtte tu naiva śāstraṃ na ca kramaḥ//

"The whole subject of embracing is of such a nature that men who ask questions about it, or who hear about it, or who talk about it, acquire thereby a desire for enjoyment. Even those embraces that are not mentioned in the Kama Shastra should be practiced at the time of sexual enjoyment, if they are in any way conducive to the increase of love or passion. The rules of the Shastra apply so long as the passion of man is middling, but when the wheel of love is once set in motion, there is then no Shastra and no order."