Thus the labour of a manufacture adds, generally, to the value of the materials which he works upon, that of his own maintenance, and of his masters profits. The labour of a menial servant, on the contrary, adds to the value of nothing.
Adam Smith (2007). “The Wealth of Nations: An Inquiry Into the Nature and Causes of the Wealth of Nations: With an introduction by Jonathan B. Wight, University of Richmond”, p.311, Harriman House Limited
