“The slow ascent of wooded hills on a sunny day”

Helmholtz, for instance, the great German physicist, speaking in 1891 at a banquet on his seventieth birthday, described the way in which his most important new thoughts had come to him. He said that after previous investigation of the problem “in all directions…happy ideas come unexpectedly without effort, like an inspiration. So far as I am concerned, they have never come to me when my mind was fatigued, or when I was at my working table….They came particularly readily during the slow ascent of wooded hills on a sunny day.”

—Graham Wallas, The Art of Thought