It is so rare to meet with a man outdoors who cherishes a worthy thought in his mind, which is independent of the labor of his hands. Behind every man's busy-ness there should be a level of undisturbed serenity and industry, as within the reef encircling a coral isle there is always an expanse of still water, where the depositions are going on which will finally raise it above the surface.
Henry David Thoreau (1817–1862), U.S. philosopher, author, naturalist. A Week on the Concord and Merrimack Rivers (1849), in The Writings of Henry David Thoreau, vol. 1, pp. 385-386, Houghton Mifflin (1906).