If you have receipts for the new furniture, with dates acquired, that will be helpful. If you have antiques you can get them appraised (expensive) or you can go online and try to get proof of what something similar is going for.
Pictures, jewellery, all those sorts of things you can research in stores and so on.

In the state that I live in (& maybe everywhere) you draw up a list of everything with what you think the value is, and the spouse can then agree or contest the worth.

Hope that helps.

Tulbagh