I like Aristotélēs (Aristole) and his writings, and browsing around his History of Animals (written circa 330 BC) I extracted some parts related to horses.
Today, I will provide you with the bulk of his horse 'quotations' from the translation by D'Arcy Wentworth Thompson and tomorrow the parts of chapter 22, 23, and 24 from Book VI of the same 'History of Animals.'
Aristotle was a keen observer, and in his search for truth and reality he strove to understand the world around him, and his notes on animals are first rate observations to be repeated, quoted or commented by various writers for the next 2000 years or so. I will quote him here, with a great pleasure :)
Well, let us begin, just note that these are Arystotle's observation (IV c BC) on the biology of horses and alike, so perhaps more interesting to those into the breeding or history of science etc. So if you are brave and willing, plunge in.