Claude Adrien Helvétius (1807). “De l'esprit; or, Essays on the mind. Transl. To Which are now prefixed, a life of the author and prefatory strictures by W. Mudford”, p.24
John Ruskin “Two paths. Lectures on art, delivered before the University of Oxford in Hilary Term, 1870. Aratra Pentelici. Time and tide. Pre-Raphaelitism. The eagle's nest. King of the Golden River. The relation between Michael Angelo and Tintoret”