I mostly agree with your criticism of my post. I was being generous trying to avoid being inflammatory here, since I know there are readers that strongly support socialist ideas (in the strict sense, not just the "safety net" sense). It was certainly Marx that pushed it so hard.

But researching this a bit, I find that it still predates Marx. I find:

Sir William Petty, 1662: "If a man can bring to London an ounce of Silver out of the Earth in Peru, in the same time that he can produce a bushel of Corn, then one is the natural price of the other."

More important, it seems that David Ricardo (a big name in economic history), in 1817 latched onto what Smith had written and states it quite definitively.