Crossbow Quick Loading Mechanism

From the time of its invention and for a very long time afterwards, the crossbow was a revolutionary invention. It was generally more powerful than an ordinary bow and, best of all, you didn't have to train for 3 years to be proficient in its use! Rather, within a week or two of practice you would be fully capable of killing a knight with it. The Pope even tried to ban the weapon from use by Christian armies (and European armies still used it anyways afterwards).
One of the major drawbacks of this weapon was that it took a ridiculously long time to load, comparable to a 16th century Arquebus. In the time that it took to fire one, a normal bowman could launch multiple arrows.

But what if, instead of people having to pull back on/crank those heavy bows, beasts of burden could've done this? Imagine the following contraption:
There's like a string thingamajig. One end is attached to a harness strapped onto a mule or a horse. The other end is attached to a crossbow, which is resting on some kind of flat surface.
The mule moves in the opposite direction, pulling back on the crossbow except with much more force than a human arm could exert. Within a matter of seconds the weapon is ready to fire.

Dassault Papillon: That's called a scorpion and it existed too.

admin: Scorpions were drawn back by horsepower?

Dassault Papillon: Well, to be fair, no, not typically. My understanding is they used a winch.