THE REASON OF THE INCREASED SIZE OF THE SUN IN THE WEST.
Some mathematicians explain that the sun looks larger as it sets, because the eye always sees it through a denser atmosphere, alleging that objects seen through mist or through water appear larger. To these I reply: No; because objects seen through a mist are similar in colour to those at a distance; but not being similarly diminished they appear larger. Again, nothing increases in size in smooth water; and the proof of this may be seen by throwing a light on a board placed half under water. But the reason why the sun looks larger is that every luminous body appears larger in proportion as it is more remote. [Footnote: Lines 5 and 6 are thus rendered by M. RAVAISSON in his edition of MS. A. “De meme, aucune chose ne croit dans l’eau plane, et tu en feras l’experience en calquant un ais sous l’eau.”—Compare the diagrams in Vol. I, p. 114.]
Taken from The Notebooks of Leonardo da Vinci edited by Jean Paul Richter, 1880.