This is one of the myths behind the discovery of alchemy....

Isis the Prophetess to Her Son Horus" from Codex Marcianus, 11th century collection of Greek fragments.

Isis tells Horus that while he was away fighting and defeating Set, she was in Hermopolis studying angelic magic and alchemy. She relates: "After a certain passing of the kairoi and the necessary movement of the heavenly sphere, it happened that one of the angels who dwelt in the first firmament saw me from above and came towards me desiring to unite with me sexually. He was in a great hurry for this to happen, but I did not submit to him. I resisted, for I wished to ask him about the preparation of gold and silver. When I put my question, he said he could not answer me since it was such a great mystery, but he said her would return next day and with him would be a greater angel, Amnael, who would be able to answer me and solve my problem. And he told me about his sign and that he would bear it on his head, and take and show me, a ceramic vessel full of shining water. He (the other angel) wanted to tell me the truth." To make a long story short – the other angel appeared and wanted to immediately "unite with her sexually." But she resisted until the angel first revealed the alchemical secret of turning base metals into gold.