Rasamanjari 6.8

6.8

ṭaṅkaṇaṃ ravidugdhena piṣṭvā mūṣāṃ ca bandhayet /
mṛdbhāṇḍe ca nirudhyātha samyaggajapuṭe pacet //

and grinding borax with calotropis milk, one should seal the crucible,
and enclosing it in an earthenware vessel, one should cook it thoroughly in an elephant-pit