The Wikipedia page on Giuseppe Peano claims the following:
At the conference Peano met Bertrand Russell and gave him a copy of Formulario. Russell was so struck by Peano's innovative logical symbols that he left the conference and returned home to study Peano's text.
However, the claim is unreferenced. Did Bertrand Russell leave the Second International Congress of Mathematicians to read Giuseppe Peano's Formulario, or is that just some myth?
Ray Monk, ‘Russell, Bertrand Arthur William, third Earl Russell (1872–1970)’, Oxford Dictionary of National Biography, Oxford University Press, 2004; online edn, May 2014 (http://www.oxforddnb.com/view/article/35875, accessed 5 Nov 2014) does not mention this premature departure:
At Paris, Russell met the Italian mathematician Giuseppe Peano, the head of a movement whose ultimate goal was to construct a single axiomatic system upon which the whole of mathematics could be founded. In pursuit of this aim Peano had invented a special symbolism which he used to construct a system of mathematical logic, at the heart of which is the now-familiar notion of a ‘propositional function’. Using this system, Peano and his colleagues had shown that arithmetic could be founded on a single elegant formal theory which used only three basic ideas (zero, number, and successor) and five initial axioms. Inspired by his meeting with Peano and his study of Peano's work, Russell returned from Paris with an almost ecstatic conviction that he knew the way ahead: if he could show that all mathematical notions were fundamentally arithmetical and that Peano's system was fundamentally a system of logic, then he would have succeeded in his stated aim of demonstrating that mathematics was logic. For this the crucial step would be to show that Peano's axioms could be founded upon a system of logic.