I had our MH weighed when new at a Moving Company that have their own scales for weighing their trailers. The scale was set perfectly with the ground so i was able to get an accurate 4 corner weight of the motorhome. I think I paid about $20
Later at an RV rally we had the Ministry of Transport on site with their portable 4 corner scales and the numbers confirmed what I had found from the original weigh in. In each case the fuel tank was almost full and the water tank was about 25%, which is the way I travel.
They also weighed the 4 corners of the Toad so I had an accurate weight for the new toad as well.