You don't even need to go that far back to run into issues, when I read Pride and Prejudice, I think Mr. Darcy was one of the richest people in England at around £10,000/year, but if you to calculate his wealth in today's terms it wasn't some outrageous sum (Wikipedia is telling me ~£800,000/year). The thing is that the economy was totally different back then -- labor cost practically nothing, but goods like furniture for instance were really expensive and would be handed down for generations.
With £800K today, you may not even be able to afford the annual maintenance for his mansion and grounds. I knew somebody with a biggish yard in a small town and the garden was ~$40K/yr to maintain. Definitely not a Darcy estate either.
Thinking about it, an income of £800K is something like the interest on £10m.