Sismondi worked hard there, with both his hands and mind, and his experiences gave him the material of his first book, "Tableau de l'agriculture toscane", which, after returning to Geneva, he published there in 1801. At a young age, Sismondi had read "The Wealth of Nations" and became strongly attached to Smith's theories. He apparently published his first work on the subject of political economy, "De la richesse commerciale ou principes de l'economie politique appliqué à la legislation du commerce" (1803) to explain and popularize Smith's doctrine, but following this Sismondi spent a considerable amount of time dedicated to historical research. He again turned his attention to political economy around 1818 when he was commissioned to write an entry on "Political Economy" for the "Edinburgh Encyclopædia". This was just following a serious economic downturn after the outbreak of the first major crisis in 1815.