Rasarnava 10.8-

10.8-

yo bāhyābhyantare śveto bahulaṃ kañcukāvṛtaḥ
taṃ vidyāt pāradaṃ devi tārakarmaṇi yojayet //
yathā kāñjikasaṃsparśāt kṣīrabhāṇḍaṃ vinaśyati
tathā hema śarīraṃ ca pāradena vinaśyati //

That which is white outside and inside, [yet] covered by thick sheaths,
know that to be mercury, O Devī; one should employ it in works for silver.
Just as a pot of milk is ruined by contact with sour gruel,
so gold and the body are ruined by [unprocessed] mercury.