"A certain amount of distrust is wholesome, but not so much of others as of ourselves; neither vanity not conceit can exist in the same atmosphere with it."

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In an atmosphere of uniform density the most distant things seen through it, such as the mountains, in consequence of the great quantity of atmosphere which is between your eye and them, will appear blue. Therefore you should make the building... wall which is more distant less defined and bluer... five times as far away, make five times as blue.

— Leonardo da Vinci