“Moreover, when much food is taken, which [i.e. the nutrient evaporation from which] the hot substance carries upwards, this latter, like a fire when fresh logs are laid upon it, is itself cooled, until the food has been digested.

For, as has been observed elsewhere, sleep comes on when the corporeal element [in the 'evaporation'] conveyed upwards by the hot, along the veins, to the head.”

— Aristotle, On Sleep and Sleeplessness (384–322 BC)

"The nights are sometimes terrible, but on the whole, I am rather better than before. I still have horrible fits of anxiety and—without knowing why—fear."

—Vincent van Gogh, Letter to Theo van Gogh (1889)

"旦耿耿也，苦不得眠，得眠不能。不冷饮，犹为患，甚无临向。书以具，不得同至，恨恨，王羲之顿首。"

—王羲之，《苦不得眠帖》（《旦罪罪帖》），303-361

—Xizhi Wang, Suffering in the Night (303-361)