Why Not Sneeze, Rose Sélavy? was an elaborate prank by Marcel Duchamp. An assisted readymade — a found object ‘enhanced’ by the artist, in this case by filling a birdcage with 152 marble ‘sugar cubes,’ a thermometer and cuttlefishbone.
The sculpture’s title references Rose Sélavy, Duchamp’s drag queen alter ego, for seemlingly no reason but the purpose of the object was helpfully clarified by Duchamp’s friend and fellow DadistAndré Breton:
“I have in mind the occasion when Marcel Duchamp got hold of some friends to show them a cage which seemed to have no birds in it, but to be half-full of lumps of sugar. He asked them to lift the cage and they were surprised at its heaviness. What they had taken for lumps of sugar were really small lumps of marble which at great expense Duchamp had had sawn up specially for the purpose. The trick in my opinion is no worse than any other, and I would even say that it is worth nearly all the tricks of art put together.”
Reed Enger, "Why Not Sneeze, Rose Sélavy?," in Obelisk Art History, Published August 15, 2017; last modified May 19, 2021, http://arthistoryproject.com/artists/marcel-duchamp/why-not-sneeze-rose-selavy/.