Artists can get away with anything

Or so it seems. The description of Duchamp's "empty" phial - or rather, the commentary about his approach to measurement - "the duality at the centre of his philosophy", indeed! - approaches, or perhaps exceeds, political spin -

"Paris Air also has a clear connection to the concept of measurement; it illustrates Duchamp's toying with the rules, or standards, of measurement. ... When reproduced on a postcard in 1937, Paris Air was identified as "Ampoule contenant 50 cc d'air de Paris." This title was mathematically inaccurate, considering the original version of Paris Air held over two times this volume of air. Typically, Duchamp embraced this inaccuracy; when issuing the edition of miniatures for the The Box in a Valise in 1941, he made sure to make them all hold 50 cc of air. However, when creating a replica of the original version in 1949 (because it had broken), Duchamp made sure to repeat the "original" size of the ampoule. This simultaneous embrace and rejection of measurement standards illustrates the duality at the center of the artist's philosophy for making art."