Sometimes, when you're deep in the countryside, you meet three girls, walking along the hill tracks in the dusk, spinning. They each have a spindle, and on to these they are spinning their wool, milk-white, like the moonlight. In fact, it is the moonlight, the moon itself, which is why they don't carry a distaff. They're not Fates, or anything terrible; they don't affect the lives of men; all they have to do is to see that the world gets its hours of darkness, and they do this by spinning the moon down out of the sky. Night after night, you can see the moon getting less and less, the ball of light waning, while it grown on the spindles of the maidens. Then, at length, the moon is gone, and the world has darkness, and rest..... ...on the darkest night, the maidens take their spindles down to the sea, to wash their wool. And the wool slips from the spindles into the water, and unravels in long ripples of light from the shore to the horizon, and there is the moon again, rising above the sea....Only when all the wool is washed, and wound again into a white ball in the sky, can the moon-spinners start their work once more....
~ Mary Stewart