The poet sings how the blood flows in his veins. He performs his functions, and is so well that he needs such stimulus to sing only as plants put forth leaves and blossoms.... His song is a vital function like breathing, and an integral result like weight.
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, p. 94, Houghton Mifflin (1906).