How To Calculate Torque To Start Drive A Four Wheel Wagon?

Bolt a lever of known length (say 1metre) radially onto the driven wheels. Add weights (the same on each lever). When the vehicle moves do the arithmetic.
Whoops sorry, that's how to measure it.
To calculate it, scribble down random numbers until you arrive at a vaguely believable figure.. .quote this figure in an authoratative voice.
Whatever you calculate will (I suspect) have little bearing on reality.
Del

If it's drawn by a single horse, it'd be 550 Ft#.