“Attributed to Thoreau, in The Life You Were Born to Live: A Guide to Finding Your Life Purpose (1995) by Dan Millman, p. xi, and to Ralph Waldo Emerson in Promotion of Pharmaceuticals: Issues, Trends, Options (1993) by Dev S. Pathak, Alan Escovitz, and Suzan Kucukarslan, p. 74, but no occurrence of it prior to the 1990s has been located.”

Source: Wikiquote