Mazur was a close collaborator with Banach at Lwów and was a member of the Lwów School of Mathematics, where he participated in the mathematical activities at the Scottish Café. On 6 November 1936, he posed the "basis problem" of determining whether every Banach space has a Schauder basis, with Mazur promising a "live goose" as a reward: 37 years later and in a ceremony that was broadcast throughout Poland, Mazur awarded a live goose to Per Enflo for constructing a counter-example.
^Mazur, S.; Schauder, J. (1937). "Über ein Prinzip in der Variationsrechnung". Comptes rendus du Congrès international des mathématiciens: Oslo, 1936. Vol. 2. p. 65.