Source, in full
As quoted in Loggers' Handbook Vol. 36 (1976), p. 72; also in North Western Reporter, Second series (1992); similar remarks have been attributed to others, including more recent attributions to Adlai Stevenson and Abraham Lincoln.
Notes from Wikiquote
I insist on being smarter today than I was yesterday. | As quoted in How to Win the Meeting (1979) by Frank Snell, p. 3