Anandakanda 1.4.166

1.4.166

evaṃ kuryād yathāśakyaṃ cāraṇaṃ parameśvari /
rase'bhraṃ cārayetpūrvaṃ catuḥṣaṣṭitamāṃśakam //

Thus one should perform assimilation according to capacity, O Supreme Lady.
First, one should cause the mercury to assimilate a sixty-fourth part of mica;