11th C horses.

[The Wizard]

Well, according to certain sources I've read, the Parthian horse was famously strong and large. Seeing as they were made to carry a heavier load than a destrier was supposed to (Parthian and Sassanid cataphracts also having horse armor), but only charged at an ambling pace, I would find it strange if the destrier (required to charge at a gallop) was smaller than this horse.

Besides that, here in the Netherlands, we still have a horse which seems to have descended from the destrier kind. The Friesian horse is a huge horse, so...