I dash out to the banks of the river [river the 'Loup', at Cagnes, France] and find myself amongst the rushes and the reeds. I grind some pigment over all this and the wind makes their slender stalks bend and appliqués them with precision and delicacy on to my canvas, which I thus offer to quivering nature: I obtain a vegetal mark. Then it starts to rain; a fine spring rain: I expose my canvas to the rain.... and I have the mark of the rain! – a mark of an atmospheric event.

In 1960; p. 61 - "Yves Klein, 1928 – 1962, Selected Writings"