Anandakanda 1.5.32

1.5.32

pūrvavacca biḍaṃ dadyādgarbhadrāvaṇameva ca /
evaṃ caturguṇe jīrṇe sūtako balavān bhavet //

And as before, one should supply biḍa and internal liquefaction; / when four times its measure is digested in this way, quicksilver becomes potent.