'But if you think that the only images that drift along

Are images that peel away from objects, you are wrong;

For there exit, as well, those that spontaneously arise,

Forming on their own in the air high in the skies

And drifting about, just as we sometimes see clouds mass together.

Mounting rapidly on high and frowning on fair weather,

Their motion ruffling the air.'

​

The Natural of Things Lucretius 50BC