The immaterial Blue colour shown at Iris Clert's in April [1958, together with Jean Tinguely] had in short made me inhuman, had excluded me from the world of tangible reality; I was an extreme element of society who lived in space and who had no means of coming back to earth. Jean Tinguely saw me in space and signaled to me in speed to show me the last machine to take to return to the ephemerality of material life.

In 1958; p. 47 - "Yves Klein, 1928 – 1962, Selected Writings"