Attributed to Aristotle in Diogenes Laertius "The Lives and Opinions of Eminent Philosophers" translated by C. D. Yonge and Henry G. Bohn (p. 188), 1853.
Orison Swett Marden (2015). “An Iron Will, He Can Who Thinks He Can & Pushing To The Front (Wisdom & Empowerment Series): How to Achieve Self-Reliance Which Leads to Vigorous Self-Faith, Personal Growth & Success”, p.591, e-artnow