Kamasutra 2.8.16

2.8.16

yuktayantreṇopasṛpyamāṇā yato dṛṣṭim āvartayet tata evaināṃ pīḍayet// etad rahasyaṃ yuvatīnām iti suvarṇanābhaḥ//

Here Suvarnanabha says that while a man is doing to the woman what he likes best during congress, he should always make a point of pressing those parts of her body on which she turns her eyes.