I discovered this amazing resource The Complete Farrier, Or Gentleman’s Travelling Companion: Comprising a General Description of the … Horse, with a Concise Account of His Diseases, Their Symptoms and Remedies …. (1809) that has a variety of helpful hints, recipes, and also an amazing guide to buying a horse!
This is a good sized chapter that starts with the general comments (Advice and Directions) and continues with specific things to look for in terms of head, moving, legs, etc. I have also snipped the “test drive” portion, because I think it also has some helpful, general hints.