A horse outputs less than 1 Horsepower.

So to pull any reasonable amount of weight, you need more horses. If you have ever looked up close at the hitchings of horse teams, 6 was the practible largest number for a single rig - remembering that wood was the primary construction material - and that 4 wheels was the normal runing gear.

So either this vehicular conveyance had lots of goodies in it, or the lady was seriously weight disadvantaged. :-)

Robin