Answer: the high taxes paid by the Third Estate
Explanation:
The Third Estate was part of the representative assembly of the Kingdom of France. There were 3 estates in the assembly and the Third Estate was at the lowest because it comprised of the common people.
The Kingdom's tax policies made it such that the First(Clergy) and the Second (Nobles) estates did not pay much taxes which meant that it was the Third Estate that were paying taxes.
The rock in this picture is meant to symbolise that tax that they paid which was then used by the First and Second Estates which are the men on top of them.
