The International Prester John Project: How A Global Legend Was Created Across Six Centuries

Essai sur les Moeurs et l'Esprit des Nations

Voltaire's "Essai sur les Moeurs et l'Esprit des Nations" (Essay on the Customs and the Spirit of Nations, and on the Principal Deeds of History, from Charlemagne to Louis XIII) references Prester John as a historical figure, a king in medieval Asia who was vanquished by Genghis Khan.