The Golden Treatise of Hermes Trismegistus, concerning the Physical Secret of the Philosopher' s Stone. In seven Sections

Understand ye then, 0 sons of Wisdom, that the knowledge of the four elements of the ancient philosophers was not corporally or imprudently sought after, which are through patience to be discovered according to their causes alld their occult operation. For their operation is occult, since nothing is done except it be compounded, and because it is not perfected unless the colours be throughly passed and accomplished.'