The Philosopher's Stone and the Virgin Mary
I will propose you a similitude of gold. The ethereal heaven was shut from all men, so that all men should descend to the infernal seats, and be there perpetually detained. But Jesus Christ opened the gate of the ethereal Olympus, and has now unlocked the kingdoms of Pluto, that the souls may be taken out; when by the co-operation of the holy spirit in the virginal womb, the virgin Mary did by an ineffable mystery and most profound sacraments conceive what was the most excellent in the heavens and on the earth; and at length brought forth for us the saviour of the whole world, who out of his super abundant bounty shall save all who are able to sin, if the sinner turn himself to him. But she remained an untouched and undefiled virgin: whence mercury is not undeservedly compared to the most glorious saint the virgin Mary. For mercury is a virgin because it never propagated in the womb of the Earth and metallic body, and yet it generates the stone for us; by dissolving heaven, that is, gold, it opens it, and brings out the soul; which understand you to be the divinity, and carries it some little while in its womb, and at length in its own time transmits it into a cleansed body. From whence a child, that is, the stone, is born to us, by whose blood the inferior bodies being tinged are brought safe into the golden heaven, and mercury remains a virgin without a stain, such as is was ever before.
-from the treatise on the alchemical art attributed to Marsilio Ficino, found on this site.