De alchimia opuscula complura veterum philosophorum, quorum catalogum sequens pagella indicabit

From this the mine generates metals, yet it cannot generate tinctures, although it well contains the full tincture in itself secretly, as the Philosopher says:

Nature contains within itself those things of which it has need, and by which it is perfected, unless it is moved by art and operation.
Therefore, in our work, art is nothing other than the assistance of nature. This is evident in many works of the arts of laymen, where nature first produces wood, secondly the burning of wood by fire is turned into ash, thirdly, art makes glass from the ash, and this is to be understood in such a way. If this first matter of glass had not been hidden in the ashes, art would by no means have made glass from it without physical nature.
How glass is in wood.

And thus consider that from no things can that be elicited which does not exist within them. Therefore, every species in its own species, and every genus in its own genus, and every nature in its own nature, naturally effects an increase of virtue and brings forth fruit according to its nature, and not in another nature contrary to it. Since every seed corresponds to its own seed, as we say regarding generation. Therefore, nothing is generated by man except a man, nor by any animal, except one like itself. And regarding the imitation of perfect nature, no art simply laboring does the ministry of nature except through the complexion a technical term for the balance of qualities of that nature. Because if an inferior foreign nature is introduced, immediately, art does not simply imitate nature. But those inferior external natures infect that nature, and immediately that which was hoped to be made is not made from it.