Turns out, it wasn't an exaggeration

From the Wiki page on rent-seeking:

The classic example of rent-seeking, according to Robert Shiller, is that of a feudal lord who installs a chain across a river that flows through his land and then hires a collector to charge passing boats a fee (or rent of the section of the river for a few minutes) to lower the chain.

There is nothing productive about the chain or the collector. The lord has made no improvements to the river and is not adding value in any way, directly or indirectly, except for ...