A porcelain urinal is the most influential work of modern art, according to a survey released Wednesday. The poll of 500 arts figures ranked French surrealist Marcel Duchamp's 1917 piece 'Fountain' an ordinary white, porcelain urinal more influential than Pablo Picasso's 'Les Demoiselles d'Avignon,' Andy Warhol's screen prints of Marilyn Monroe and 'Guernica,' Picasso's searing depiction of the devastation of war. Duchamp pioneered the use of everyday objects as art, an aesthetic that questioned the nature of art itself.