It is impossible to step into the same river twice.
(Heraclitus (c. 535-475 B.C.), Greek philosopher. Diels-Kranz, fr. 91 (from Plutarch).
Heraclitus, one of the two or three most influential philosophers before Socrates, was known as "the riddler" or "the obscure.")
He who hears the rippling of rivers in these degenerate days will not utterly despair.
(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. 356, Houghton Mifflin (1906).)