Possibly SoL might be referring to Mises’s remarks in “Economic Policy” on p. 2:
“However, as the rural population expanded, there developed a surplus of people on the land. For this surplus of population without inherited land or estate, there was not enough to do, nor was it possible for them to work in the processing industries; the kings of the cities denied them access. The numbers of these “outcasts” continued to grow, and still no one knew what to do with them.”
He then goes on to say that some of these outcasts created small workshops and that these were the origins modern of capitalism.
What I can’t understand is why the population continued to increase if these “outcasts” had nowhere to go and nothing to do, given the rigid social structure and the pre-industrial nature of society.