Anandakanda 2.2.26

2.2.26

aṣṭabhiśca puṭairhema mriyate pūrvavatkriyā /
<svarṇabhasma (3)>
śuddhasūtasamaṃ svarṇaṃ khalve kuryācca golakam //

through eight firings in a pit, gold is killed by the procedure described before.
Gold ash (3):
One should make a ball in a mortar of gold equal to purified mercury;