Anandakanda 1.7.89

1.7.89

brahmaviṣṇvīśabhūtātmamātṛkāḥ parikīrtitāḥ /
pītavarṇaṃ sparśavedhi kṛṣṇaṃ śreṣṭhaṃ rasāyane //

declared to be Brahmā, Viṣṇu, Īśa, Bhūtātman, and the Mātṛkās.
The yellow-colored variety transmutes by touch; the black is best in rejuvenation therapy;