I live here in Paris. I rise every day at five o'clock; I drink my two large glasses of hot water; I take my coffee; I write when I am alone, which is rare; I do my hair in company; I dine every day with the king, chez lui, or with him and les seigneurs. I make calls after dinner; I go to the theater; I return to my place at ten o'clock; I drink my hot water; and I go to bed. And in the morning I begin all over again. I eat so little at these great dinners that I am often obliged to drink a third glass of water to appease my hunger. I owe to the severity of this diet my good health. I will be faithful to it until I die.
Letter to her daughter, July 8th, 1766. Translated and cited by Dena Goodman, The Republic of Letters: A Cultural History of the French Enlightenment.
(Thanks to Iris Key.)