"On the Happy Life". Essay by Seneca the Younger (58 AD); later published in Sir Edward Bulwer-Lytton "Caxtoniana: A Series of Essays on Life, Literature, and Manners", p. 174 (in the essay "The Sympathetic Temperment"), 1863.
"Epistolæ Ad Lucilium" by Marcus Fabius Quintilianus as reported in "Hoyt's New Cyclopedia Of Practical Quotations" by Jehiel Keeler Hoyt, p. 878-82., 1922.