As I've said before, a couple of my brothers clients drag their light planes arround with dirty old coxes......admittedly a single engined plane will be a bit lighter than a decent sized boat or caravan.
But the hydrostatic drive in some of the later mowers should manage it particularly in low gear on the flat.
Those big old walk behind slashers were a piece of work......I recon that would be worth poking with a stick.
Another thaught has just come to me.
Rotary cultivators or chain diggers.....often the same machine with a different impliment.
Now they have a decent amount of pull and some weight along with it.
After the cultrual revolution, the cheineese built thousands or rotary cultivators and thay used them as a mechanical replacement for the ox or donkey.....
I've seen pictures and video of em towing huge trailers with the things.
cheers