Adam Smith (1776):
No equal capital puts into motion a greater quantity of productive labour than that of the farmer.
After agriculture, the capital employed in manufactures puts into motion the greatest quantity of productive labour, and adds the greatest value to the annual produce. That which is employed in the trade of exportation, has the least effect of any of the three.
In modern language, we might write the above as
Has there been any research proving/disproving the above assertion (in the context of 18th-century Britain)?