If we are including trailers, then how about:
a 1000 litre water tank (empty):
a 100 litre water tank (full!)
a boat:
1/4 ton of hoss muck
Last week I had some 3.6 metre lengths of 6" x 2" timber on the same trailer.
And I have riden about a mile home, carrying a 8' x 4' sheet of plywood under my arm with just a bungee cord as a handle!