The belief of the alchemists that all natural events are connected by a hidden thread, that everything has an influence on other things, that "what is above is as what is below," constrained them to place stress on the supposed connexion between the planets and the metals, and to further their metallic transformations by performing them at times when certain planets were in conjunction.
The seven principal planets and the seven principal metals were called by the same names: _Sol_ (gold), _Luna_ (silver), _Saturn_ (lead), _Jupiter_ (tin), _Mars_ (iron), _Venus_ (copper), and _Mercury_ (mercury).

The author of _The New Chemical Light_ taught that one metal could be propagated from another only in the order of superiority of the planets.

He placed the seven planets in the following descending order: Saturn, Jupiter, Mars, Sol, Venus, Mercury, Luna.

"The virtues of the planets descend," he said, "but do not ascend"; it is easy to change Mars (iron) into Venus (copper), for instance, but Venus cannot be transformed into Mars.
Although the alchemists regarded everything as influencing, and influenced by, other things, they were persuaded that the greatest effects are produced on a substance by substances of like nature with itself.

Hence, most of them taught that the seed of metals will be obtained by operations with metals, not by the action on metals of things of animal or vegetable origin.