Who Were the Richest People in History?

Some people have an obscene amount of wealth. But how do you compare rich people in different eras? maybe by comparing them with the other people of that same era, or maybe by adjusting for inflation. Simon Whistler of Today I Found Out makes things easier by naming the wealthiest person of each century. And it's still relative. Sure, Genghis Khan was a fabulously wealthy man, but he lived in a tent. Mansa Musa had tons of gold, but no air conditioning. But at least they didn't worry about covering the rent.