Kautilya's Arthashastra 2.13.18

2.13.18

samarāgalekham animnonnate deśe nikaṣitam, parimṛditaṃ parilīḍhaṃ nakhāntarād vā gairikeṇāvacūrṇitam upadhiṃ vidyāt //

Whenever a uniform streak made on the even surface of a touch-stone can be wiped off or swept away or when the streak is due to the sprinkling of any glittering powder (gairika) by the nail on touch-stone, then an attempt for deception can be inferred.