"When moving on a curved line - this includes all turns on one track - the horse must be a part of this line. It must be bent in its body to the extent required by the curve. The degree of the required bend depends on the size of the circle on which the horse moves, the smaller the circle, the greater the bend. This bend must extend over the entire spinal column so as not to have an adverse effect on the horse’s way of going."
(Gustav Steinbrecht, 1884)