The unofficial world records are 8'3", jumped by a horse called Heatherbloom in 1902, and 8'3 1/2", jumped by King's Own in the 1920s.
The official world record belongs to a horse called Huaso in 1949. Amazingly, film of this still exists and is on YouTube:
That's a 60 year old record, right there. High jump has fallen out of favour in recent years, and was only ever featured as an Olympic sport once - in 1900. It's perhaps not surprising that these records are all old - the rise of the animal rights movement has put safeguards on these kind of sports that reduce the risks people are willing to take with their animals, and fair enough. What that film of Huaso doesn't show is the horse that was competing against him, that crashed through the fence, fell and was injured and had to be retired. What you can see if you look closely in both vids is the flexing of the horse's fetlock joints as it lands from that height with a rider.
But all that aside, HOLY FUCK what a feat. The thing that blows me away is those fences are solid. Neither the horse nor the rider can see what's on the other side, and the horse must trust that the landing will be ok in order to fling itself up there. I'm.. astounded.
Actually, come to think of it, my pony when I was a kid was one of those that would go "GERONIMO!" and charge furiously at anything I pointed him at, without hesitation, whether he'd seen the other side or not. But I never jumped him higher than 4'6".
In other news, boys get all the fun stuff. In the bathroom this morning looking for hair product, found a tin with a spaceman on the lid. How come girls don't get tins with spacemen on them? I mean look:
And it's called Guck-in-a-Puck. Seriously, I'd buy that just for the name - but given that I woke up this morning looking like a troll doll and now my hair is relatively presentable, it's a good product too. C'mon ladies hair product makers - get with the program. We don't all take ourselves that seriously...
And.. ferrouswheel is once again off gallivanting round the globe - this time it's San Francisco and he gets Extra Bonus Wednesday. He also gets to go into the Googleplex. I am Teh Envious. Clearly I need to become a boffin.. although somehow I think the social policy academic travel would be a lot drier than the AI stuff. Damn. *goes to learn python*