"When the whole winter and part of the spring were over, the general chiselling began. This was the hardest work. It did not consist only in revising the surfaces, which had to become increasingly tense and turgid, and in bringing back to the surface the inner part of the material (which, once it had been chiselled, would start vibrating with the gleams of the marble flakes contained in it). It was also a work that led us to get to grips, on the spot and directly on the material, with new problems created by local factors: light, space, colour, three-dimensional perspective, the constant movement of the light, the sun, the passage of clouds, the overcast sky.