Kamasutra 2.7.32

2.7.32

svapneṣv api na dṛśyante te bhāvās te ca vibhramāḥ/
suratavyavahāreṣu ye syus tat kṣaṇakalpitāḥ//

Such passionate actions and amorous gesticulations or movements, which arise on the spur of the moment, and during sexual intercourse, cannot be defined, and are as irregular as dreams. A horse having once attained the fifth degree of motion goes on with blind speed, regardless of pits, ditches, and posts in his way; and in the same manner a loving pair become blind with passion in the heat of congress, and go on with great impetuosity paying not the least regard to excess. For this reason one who is well acquainted with the science of love, and knowing his own strength as also the tenderness, impetuosity, and strength of the young woman, should act accordingly. The various modes of enjoyment are not for all times or for all persons, but they should only be used at the proper time, and in the proper countries and places.