Augustin Cournot (1801–1877) was a 19th-century French economist who pioneered the use of mathematics in economic analysis. In his 1838 book, 'Recherches sur les Principes Mathématiques de la Théorie des Richesses,' he developed a foundational model of oligopoly and also analyzed monopoly pricing. A notable example from his work is the case of a mineral spring with unique properties, which he used to demonstrate that a monopolist selling a differentiated product would maximize profit by setting a price above the marginal cost of production. His work influenced later prominent economists like Marshall and Walras.