When Yves Klein released The Immaterial Zone, the work comprised documentation of ownership of empty space.
Taking the form of a cheque, in exchange for gold; the buyer could then complete the piece in an elaborate ritual in which the buyer would burn the cheque, and Klein would throw half of the gold into the Seine.
The ritual was performed in the presence of an art critic or distinguished dealer, museum director and two appointed witnesses.

After the creation of the piece in 1959 eight Zones were sold.
“Klein’s receipts verify the existence of an invisible work of art, which prove that a formal sale has taken place. As Klein established in his ‘Ritual Rules’, each buyer has two possibilities; If he pays the agreed amount of gold in exchange for a receipt, Klein keeps all of the gold, and the buyer does not really acquire the “authentic immaterial value” of the work. The second possibility is to buy an immaterial zone for gold and then to burn the receipt. Through this act, a perfect, dematerialization is achieved. Klein seeks to ultimately demonstrate the indefinable, incalculable value of art.