The Wealth of Nations by Part 1 Chapter 7 Page 10

stock in preparing and bringing it to market. The quantity brought thither will soon be sufficient to supply the effectual demand.

All the different parts of its price will soon sink to their natural rate, and the whole price to its natural price.

The natural price, therefore, is, as it were, the central price, to which the prices of all commodities are continually gravitating. Different accidents may sometimes keep them suspended a good deal above it, and sometimes force them down even somewhat below it. But whatever may be the obstacles which hinder them from settling in this centre of repose and continuance, they are constantly tending towards it.

The whole quantity of industry annually employed in order to bring any commodity to market naturally