A summary of How To Buy A Young Horse from Xenophon The Art of Horsemanship.
How to Buy a Young Horse:
Xenophon opens his treatise with the assumption that the reader is to purchase a young horse, as yet untrained.
It is in this chapter that he makes the first reference to the lost treatise by Simon.

As his recommendations for purchasing a young horse, Xenophon details the strengths the animal should possess and the flaws that should be avoided.
What we are given is the image of an attractive but compact animal, with a strong, heavy body and neck, small head, and long legs. The hooves are to be strong as well, with thick walls and curved soles.
Xenophon warns against purchasing a horse whose legs are too straight or too sharply angled, citing these faults as weaknesses that will lead to frequent inflammation and other infirmities of the legs.
He also warns against purchasing a horse with a hollow hoof, though it is somewhat unclear what he means by this.
Marchant, in his translation, notes that though Xenophon warns against the purchase of horses whose hocks are angled inward, animals with this conformation are often good trotters. Nevertheless, this type of angle in the legs is still considered a conformation fault by the modern rider.