The Da Vinci Notebooks at sacred-texts.com
A luminous body when obscured by a dense atmosphere will appear smaller; as may be seen by the moon or sun veiled by mists.
Of several luminous bodies of equal size and brilliancy and at an equal distance, that will look the largest which is surrounded by the darkest background.
I find that any luminous body when seen through a dense and thick mist diminishes
in proportion to its distance from the eye. Thus it is with the sun by day, as well as the moon and the other eternal lights by night. And when the air is clear, these luminaries appear larger in proportion as they are farther from the eye.