Kamasutra 2.2.19

2.2.19

rāgāndhāv an:apekṣitātyayau parasparam anuviśata ivotsaṅga-gatāyām abhimukhopaviṣṭāyāṃ śayane veti [4] kṣīra-jalakam.

(4) When a man and a woman are very much in love with each other, and, not thinking of any pain or hurt, embrace each other as if they were entering into each other's bodies either while the woman is sitting on the lap of the man, or in front of him, or on a bed, then it is called an embrace like a "mixture of milk and water."