Brancusi as copper

Interesting story from this article on Calatrava in the New Yorker.
In 1926, Marcel Duchamp tried to bring in a sculpture of Brancusi, a bird in copper, for an exhibition. When it arrived at customs, the officials said, ‘You have to pay a duty on copper entering this country.’ The organizers of the exhibition said, ‘But this is a piece of art,’ and the customs said, ‘No, this is a piece of copper.’ Brancusi won.”