Truck and Barter

I don't remember writing this paragraph, or even thinking about it:

Let's examine the price of wheat in Smith’s Wealth of Nations--an extensive historical series compiled from one major source and many minor sources. We ask a simple question, "what are these prices supposed to represent?" The median exchange price, the mean exchange price, the first or last price of the year, the average price on a certain day? What is the error in this data? What does this imply about markets, people, processes, end states (equilbria), welfare, statistical procedure?

That's an entire dissertation in itself.