Bob taught Prez to pull a cart with essentially that. It was a sled so in the dirt and sand it created quite a drag.
He was a chubby old pony, so he wasn't likely to get his leg over the traces, kick the cart to pieces, and gallop off trailing bits of harness . . . but you never know.
My mare is singularly unsuited to harness, being very tall, very leggy, and very narrow.