Not much. Consider the construction. The hoppers are sheet metal; volume yes, weight no. The rest is frame work, heavy, but not much volume.
I'd guess if you got to 1000# you'd be lucky. Mine is tongue heavy as the tires are in alignment with the hopper and everything else is resting on the tongue. Regardless I can pick up the tongue by hand and connect it to the draw bar. Guess tongue weight at not more than 75#.
I can put 6-50# bags of seed in it and my 30 hp Ford doesn't know anything is behind it.