Kautilya's Arthashastra 14.2.6

14.2.6

etayor anyatarasya mūtraleṇdarasasiddhaṃ siddhārthakatailam arkatūlapataṅgacūrṇapratīvāpaṃ śvetīkaraṇam //

The oil prepared from mustard seeds which have been previously kept in the urine and fluid dung of any of the two animals, a white goat and a white donkey, causes (when applied) such white colour as that of the fibre of arka plant or the down of a (white) bird.