Anandakanda 2.7.63

2.7.63

sasatvaṃ nirmalībhūtaṃ lohakhalve vicūrṇayet /
mardayet triphalākvāthair yāmaṃ gharme viśoṣayet //

That essence having become spotless, one should pulverize it in an iron mortar; / one should grind it with decoction of triphalā for a watch and dry it in the sun.