When the alchemists speak of working with the sun and the moon, they are not referring of course to the two planets that we can see in the sky, but to the two symbols of the masculine and feminine principles which are active throughout creation and within the human being itself.
True alchemy is spiritual alchemy, and the two principles with which we must work are the will (the sun) and the imagination (the moon). Through the will and the imagination, a disciple is able to transmute his own matter and to become, symbolically, like the sun and the moon, or radiant and pure. It is not by chance that in astrology, Aries is the domicile of Mars (masculine principle) and Taurus is the domicile of Venus (feminine principle).
For it is by working with the sun and the moon to sublimate the sexual force (Venus) and the dynamic, active energy of the will (Mars) that the alchemist obtains all the spiritual powers symbolised by Mercury, the agent of magic.
Omraam Mikhael Aivanhov