Then the voice told her how by a certain cave she might reach the realms of Pluto, and how to avoid all the dangers of the road, to pass by Cerberus, the three-headed dog, and prevail on Charon, the ferryman, to take her across the black river and bring her back again. But the voice added, "When Proserpine has given you the box, filled with her beauty, of all things this is chiefly to be observed by you, that you never once open or look into the box nor allow your curiosity to pry into the treasure of the beauty of the goddesses.