Rasaratnasamuccaya 5.62

amlaparṇīṃ prapiṣyātha hyabhito dehi tāmrakam /
samyaṅ nirudhya bhāṇḍe tamagniṃ jvālaya yāmakam /
bhasmībhavati tāmraṃ tadyatheṣṭaṃ viniyojayet //