I'm assuming your question was the how?
In practical terms it is impossible to cap or put a ceiling on wealth, other than the point that available wealth at any one time is a finite resource, although many will disagree with that,
if you want to get into the tax argument there is already low hanging fruit. By making companies declare what they actually earn would be a start, tax earnings at point of earnings is another. You have to bear in mind as well that when the US economy was at its strongest it had a marginal tax rate of 92%. The latest agreements at the G20 where all companies should pay at least 15% is literally allowing big global companies a free hit against smaller companies, who will be paying 25, 30 or 40%. Historically I've been in favour of a flat tax rate across the board but ive changed my mind on that recently due to the reasons below.
Assets could be taxed, every company declaring a value of lets say a quarter of a billion would get a wealth tax of lets say 0.5% of that wealth, 1 biliion its 1%, 2 billion 2% or something similar. This isn't just to raise tax revenue, I think it would be useful in reigning in ridiculous asset values in general. Also one idea I have is that productive and non productive earnings are taxed at different rates with non productive earnings taxed on a sliding scale upwards to something fairly high 60-70% maybe, whilst productive earnings are taxed at a standard rate across the board. The other part of this is how finance and banks are taxed - lending for non productive purposes ie the aquisition of assets should be taxed at a fairly high rate, as well as being subject to capital gains. This firstly raises tax revenue and should push economies back towards productive means rather than being geared for rentier models.
There would have to be rules built in for innovators, and rules for those people who build productive companies, that employ people and actually create wealth.
Individuals in my opinion should have a flat tax rate across the board with much stronger limits on avoidance.
An individual country would need to do it because global systems are fundamentally tied into a libertarian, privatisation heavy, supply side economic model. If an individual country was to do that and lets say big global firms pulled out, that economy still has economic needs - the country would be forced to look inwards for its productive capacity. It's pie in the sky of course because there isn't a single western indutrialised nation that has a government that a) has the inclination to change the systems and b) the basic competence (in most cases).