A "surtax" of 4% on income over $1MM in a year. Or whatever % makes sense, but such that the really high levels of income beyond what 99.9% of the population could ever make in a year gets a healthy tax rate.
I don't like Wealth Tax as a concept. The money was already taxed at least once, and likely more via Capital Gains. It's just stealing. Increase the marginal rates to levels that Reagan actually brought it "down" to, and you get the same effect. Taxing what some activist or politician determines is "wealth" at some arbitrary percentage is a really ugly slippery slope.