Kautilya's Arthashastra 2.13.58

2.13.58

tīkṣṇatāmrasaṃskāraṃ ca budhyeta //

Before these varieties of gold are put to use, their test streak shall be taken on touch-stone. The process of assaying tíkshna and copper shall be well understood. Hence the various counterweights (avaneyimána) used in weighing diamonds, rubies, pearls, corals, and coins, (rúpa), as well as the proportional amount of gold and silver necessary for various kinds of ornaments can be well understood.