Anandakanda 1.26.200

1.26.200

śulbe jalanibhā tīkṣṇe śuklavarṇā praśasyate /
yantram evauṣadhībhyaḥ syācchreṣṭhaṃ sūtasya yantraṇe //

in copper, water-like [appearance is praised]; in cast iron, a white color is praised.
An apparatus alone is superior to medicinal herbs for restraining quicksilver;