Got any plate glass windows or a mirror big enough to check?
Use something 'known flat' to measure the deviation in the floor? Good idea. Will have a think. I have a very large glass tabletop desk but it weighs a tonne and all my stuff is on it...but I'm sure there's other stuff we could use.
We bought some nice chairs.
They arrived. They are nice. But they rock. In a bad way.
Is it possible that half an inch between the bottom of a leg and the floor can be attributed to our (admittedly somewhat shonky) floor?