coffin bone
This is the main bone inside a horse's hoof. I don't know why it's called that, but you can see some pictures here:
http://www.barefoothorse.com/ Please click on Photo Gallery; apparently this site will only let you link to the home page.

his front legs cantered and his back ones paced. Whoa, I'll bet that was weird!
Faldage, your Welsh pony story intrigued me. Would you mind supplying a few more details, such as how the wineglass could get on her back with no human involved?