"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.
Robert Louis Stevenson (2015). “Collected Memoirs, Travel Sketches and Island Literature of Robert Louis Stevenson: Autobiographical Writings and Essays by the prolific Scottish novelist, poet and travel writer, author of Treasure Island, The Strange Case of Dr. Jekyll and Mr. Hyde, Kidnapped & Catriona”, p.288, e-artnow