This paper analyzes the first attempt to introduce in Portugal economic studies based on a neoclassical approach. In 1910 António Horta Osório wrote a textbook, A Mathematica na economia pura [Mathematics in pure economics], in the context of an attempt to obtain the chair of Political Economy at the Lisbon Polytechnic School. He did not receive the appointment, and although the book was translated into French, under the title Théorie mathématique de l'échange, and praised as a good elementary presentation of the basic framework of the general equilibrium theory of Léon Walras and Vilfredo Pareto, it had almost no effect on the Portuguese intellectual scene. Neoclassical economics would only become a standard paradigm in Portuguese universities in the 1940s. This paper explains why his name faded from the intellectual scene in Portugal and elsewhere.