Source: SB 5.24.17 Purport

Srila Sanatana Gosvami also states that when bell metal is treated with mercury, it can produce gold. Srila Sanatana Gosvami mentions this in regard to the initiation of low-class men to turn them into brahmanas. Sanatana Gosvami said:

yatha kancanatam yati
kamsyam rasa-vidhanatah
tatha diksa-vidhanena
dvijatvam jayate nrnam

“As one can transform kamsa, or bell metal, into gold by treating it with mercury, one can also turn a lowborn man into a brahmana by initiating him properly into Vaisnava activities.” The International Society for Krishna Consciousness is trying to