Anandakanda 2.1.145

2.1.145

peṣaṇaṃ gharmapākaṃ ca sthālīpākaṃ puṭaṃ kramāt /
kuryāccatvāri karmāṇi ṭaṅkaṇaṃ ca puṭe puṭe //

Trituration, sun-heating, cooking in an earthen vessel, and calcination in succession: / One should perform these four operations, adding borax at each calcination.