This letter to the editor (with, I am assuming a pseudonym) appeared in the March 1800 issue of The Sporting Magazine.
Judging from some other references, I am thinking this might refer to a practice of “low wheeling” carriages:
Cursory Remarks on the Subject of Wheel Carriages (1817)
In the sporting science world, I also found some debate on the efficiency of a low versus a high carriage.