Friedrich von Krane, captain and squadron commander in the 4th Prussian cuirassier regiment, published an excellent training manual in 1856, entitled "Die Dressur des Reitpferdes (Campagne- und Gebrauchs-Pferdes) mit Ruecksichtnahme auf die Ausbildung von Soldatenpferden in Abteilungen." In this book, he analyzes in great detail the different conformation features of the haunches, back, forehand, and neck and their influences on the horse's movement and training. He describes the gymnasticization of the neck, the back, the haunches, and front legs separately in the first part of the book. The second part contains a progressive account of the horse's training beginning with a green horse and ending with advanced campaign school exercises, the jumping of obstacles, and certain observations about horses in the military.
In the chapter of the lateral movements, von Krane establishes interesting correlations between the conformation type and the preference for shoulder-in related movements versus travers-related movements.
p.225f.:
"I have made the experience that short horses with an inflexible back and inflexible haunches prefer the shoulder-in over the travers - and vice versa, long horses with flexible haunches prefer the travers over the shoulder-in. I do not believe that the fact that the haunches travel on a smaller circle in the travers, while the forehand is on a larger circle, is the only reason for the increased flexion of the haunches in the travers, since on straight lines both travel the same distance. However, the horses' preferences remain unchanged. "I believe, instead, that the haunches are less weighted in the shoulder-in, where the load falls more onto the outside legs, i.e. against the bend of the rib cage, than in the travers, where it falls into the bend of the rib cage. The increased weighting of the hind legs in the travers may also have to do with the fact that the horse's head position and the rider's weight coincide in it, whereas they differ in the shoulder-in. "This leads me to conclude that long, flexible horses should begin the travers as the easier movement, while short, inflexible ones should start with the shoulder-in. "Counter-shoulder-in and renvers are variations which do not change anything, except that they grant the advantage of the wall, or the inside of the arena, respectively. "If one wants to correct without stronger rein aids a horse who rushes in the shoulder-in, one takes him into a counter-shoulder-in with the same bend. The wall will form a natural obstacle and grant the advantage that the animal will shift his weight backward on his own, for which I would have to use different means otherwise. I can therefore use the forward driving calf energetically, without having to use equally strong rein aids. In horses who are being taught to step under with their hind legs, but whose overly flexible hocks make active rein aids unadvisable, this advantage is undisputable. "On the other hand, if a horse sucks back in the travers, and one wants to make him advance more with the inside calf, one takes him into the renvers. This gains the open arena, while maintaining the same bend. ... "The counter-shoulder-in also has the advantage in teaching younger riders that it brings the laziness of the outside leg, which destroys the usefulness of the shoulder-in, out into the open, because the wall is often the only reason why older horses do not suck back at every stride. It should therefore be practiced diligently. In my opinion, one cannot invent enough variations that require a change in the aids, as soon as the seat has been acquired and the aids have to be taught, so that the latter become so ingrained in the rider that the thought 'do' makes the intermediate thought 'do how?' superfluous. It is only through practice that such a skill level can be reached that hand, leg, and weight support each other correctly, and never contradict each other in their timing or their strength. Even if counter-shoulder-in and renvers were no more than such variations, that lead to new transitions, they would always be advantageous."
