— Socrates classical Greek Athenian philosopher -470 - -399 př. n. l.
As reported by Charles Simmons in A Laconic Manual and Brief Remarker, containing over a thousand subjects alphabetically and systematically arranged (North Wrentham, Mass. 1852), p. 103 http://books.google.de/books?id=YOAyAQAAMAAJ&pg=PA103&dq=socrates. However, the original source of this statement is unknown.
Cf. Joseph Addison in The Spectator No. 574 Friday, July 30, 1714, p. 655 http://books.google.de/books?id=K1cdAAAAMAAJ&pg=PA655&dq=socrates: In short, content is equivalent to wealth, and luxury to poverty; or, to give the thought a more agreeable turn, "content is natural wealth," says Socrates: to which I shall add, "luxury is artificial poverty.".