Here's something that you probably didn't know: horses can sit. No, really. They can. I was just as surprised as you are.
My limited interaction with horses has lead me to believe that these guys just stand all the live-long-day. After all, have you ever driven past a farm field and seen one just casually sitting to admire the beautiful scenery? No, not you haven't. And if you said you have, I don't think you're being totally honest with yourself.
As impossible as it is to believe, horses do actually sit sometimes. And there's even a viral photo to prove it.