Quesnay was a French physician (1694-1774), who also studied economic issues, and was the true founder of the economic doctrine known as Physiocracy. His early works were written in the Encyclopédie of Diderot and d’Alembert (1756,1757). However, his most important contribution to economics was his famous Tableau Économique, 1758, the first circulatory diagram, allowing a further understanding of how an economy works. He did it by comparing the income flow of a given country to the blood in the human body.
The tableau allowed further developments in the matter, such as Léon Walras’ general equilibrium and Wassily W. Leontief’s input-output model.