What then is, generally speaking, the truth of history? A fable agreed upon.

Conversation with Emmanuel, comte de Las Cases (20 November 1816), Mémorial de Sainte Hélène, v. 4, p. 251. However, the phrase predates Napoleon. Helvétius attributes it to Bernard le Bovier de Fontenelle, De l'esprit (1758), p. 443