Rasahridayatantra 5.8

Salt flooded with juice of devī and betel leaves pulverized on a stone,
well-calcined after three firings: one should place this in an iron vessel.

A clear, wide cup is fashioned half a digit deep as the lower support,
and above it, a cup one digit in height should be placed.

Fitted with three holes, it is suitable; iron rods are to be inserted
into the holes four digits above, and gold leaves are also placed there.

Having positioned them, they are fumigated; one should kindle a fire beneath the apparatus;
merely by the smear of smoke, the gold leaves turn black.

Heated by fire and subsequently killed by smoke in the apparatus,
by the process of cooked gold, the king of mercuries assimilates and melts in the interior.