obsession with the limits of physicality, whilst parodying the Art World's obsession with permanence, and also provided a poignant Memento Mori. Artist's Shit In May 1961 Manzoni created 90 small cans, sealed with the text Artist's Shit (Merda d'Artista). Each 30-gram can was priced by weight based on the current value of gold (around $1.12 a gram in 1960). The contents of the cans remain a much-disputed enigma, since opening them would destroy the value of the artwork. Various theories about the contents have been proposed, including speculation that it is plaster. In the following years, the cans have spread to various art collections all over the world and netted large prices, far outstripping inflation. A tin was sold for € 124,000 at Sotheby's on May 23, 2007; in October 2008 tin 83 was offered for sale at Sotheby's with an estimate of £ 50–70,000. It sold for £97,250. It was described as: On October 16, 2015, tin 54 was sold at Christies for the astonishing sum of £182,500. The tins were originally to be valued according to their equivalent weight in gold – $37 each in 1961 – with the price fluctuating according to the market. Other works from this period include limited edition thumbprints, and the Declarations of Authenticity, 1961-61, a printed multiple that could be bought, proving the owner's status as either part or whole work of art, depending on the price paid. He also designated a number of people, including Umberto Eco, as authentic works of art gratis. Various other experimental pieces by Manzoni included trying to create a mechanical animal as a moving sculpture and using solar energy as a power source. In 1960 he created a sphere that was held aloft on a jet of air. Other works Magic Bases (Magisk Sockkel, 1961), a series of wooden plinths that could be stood on to acquire status of 'Living Sculpture'. Lines of Exceptional Length (1960–61). Lines drawn on paper, the longest of which was 7.2 km, intended to be left in every major city in the world, which would equal the length of the equator when joined. Base of the World (Socle du Monde, 1961). A large metal plinth, inscribed 'The Base Of The World, Homage To Galileo' placed upside down in a field in Herning, Denmark. It announces that the whole world is a work of art, rendering the artist obsolete. Piero Manzoni; The