In 1961 Italian artist Piero Manzoni offered art buyers 90 tins of his own excrement, signed and numbered, each sold by weight at gold’s daily market price.

That would have been a good investment. A tin that would have cost $37 in 1961 was auctioned by Sotheby’s for $67,000 in 1991 — outperforming gold more than seventyfold.