Kautilya's Arthashastra 14.2.4

14.2.4

śvetabastamūtre saptarātroṣitaiḥ siddhārthakaiḥ siddhaṃ tailaṃ kaṭukālābau māsārdhamāsasthitaṃ catuṣpadadvipadānāṃ virūpakaraṇam //

The oil prepared from mustard seeds previously kept for seven nights in the urine of a white goat will, when used (externally) after keeping the oil inside a large bitter gourd for a month and a half, alter the colour of both biped and quadruped animals.