We think we know what it means to be wealthy. We have Bill Gates and Paris Hilton showing us the broad spectrum of what happens to humanity when faced with a fortune. However, we haven't seen the half of it. A new study has adjusted wealth to take account for inflation - and revealed the 25 richest people who ever lived
So why were they so rich, how did they make it - and how did they spend it?
The list, published by www.celebritynetworth.com, adjusted the figures to take account of inflation. The difference it makes is dramatic. So, for example, $100 million in 1913 is equal to around $2.3 billion today. It means only 3 of the top 25 are alive today.
1. Mansa Musa I of Mali emerged as the richest man of all time. He ruled West Africa in the 14th century, and had almost three times the wealth of Bill Gates - at $400 billion.
He was born in 1280 and his empire covered Ghana, Timbuktu and Mali. His huge wealth was partially founded on production of valuable resources: namely salt and gold. However, shortly after his reign, it all fell apart with civil war and invasions breaking up the empire.
It all started with canny Mayer Amschel Rothschild, who set up a banking house in the 18th century, and sent his five sons to each of the five major European banking centres to build a dynasty.
3. John D. Rockefeller, is best-known as the richest-ever American - worth $340 billion in today's money. At the time he was known for being the world's first billionaire.
His vast wealth was built on an oil empire, which netted him an astonishing fortune. He then did what every self-respecting billionaire should consider - he spent the last 40 years of his life in retirement, establishing charitable foundations across medicine, science and education.
4. Andrew Carnegie, worth $310 billion, made his money in American steel. He was another 19th century industrialist who devoted his latter years to philanthropy - and gave away every penny he had made.
5 Tsar Nicholas II of Russia, a 19th century Tsar, worth $300 billion. His vast wealth, unfortunately, spelled the end of him and his family. They were murdered by Bolsheviks shortly after his abdication in 1917, and their empire was taken apart.
6. Mir Osman Ali Khan, worth $236 billion. The ruler of Hyderabad in the 19th and early 20th century - until the area became part of India. Much of his vast wealth was held in gold, and he owned over $400 million of jewels.
7. William the Conqueror, Norman knight, turned ruler of England after the invasion of 1066.
He was worth $229.5 billion. The riches that came with ruling were clear. However, so were the challenges at that time, and he died in battle.
8. Muammar Gaddafi, worth $200 billion. The website claims that the true extent of his enormous wealth surfaced after his capture and death last year. Much of this was in cash in overseas bank accounts, as well as extraordinary wealth in the trappings of supreme power.
9. Henry Ford, worth $199 billion. This 19th century industrialist and pioneer of the production line revolutionised travel, and left an astonishing sum to the Ford Foundation - still controlled by his family.
10. Cornelius Vanderbilt, worth $185 billion. Much of his vast wealth was built on the American railroads.
11. Alan Rufus, worth $178.65 billion. Companion of William the Conqueror. He was rewarded for his support with vast swathes of England.
12. Bill Gates, worth $136 billion, and the second richest man alive today. He remains the largest shareholder of Microsoft, but now devotes much of his energies to extraordinary philanthropy through the Bill and Melinda Gates Foundation. His current goal is to eradicate Polio worldwide.
13. Wiliam De Warenne, worth $146.13. The first Earl of Surrey was worth a small fortune in the time just after the Norman Invasion, where his enormous landowning formed the basis of his wealth.
14. John Jacob Astor, worth $121 billion. Fur trader turned New York real estate mogul, who used part of his vast wealth to develop the beginnings of the New York Public Library.
15. Richard Fitzalan, worth $118.6 billion, another landowning British Nobleman, this time born in 1306.
16. John of Gaunt, $110 billion. The third son of Edward III, who relied on enormous land grants for his fortune.
17. Stehen Girard, worth $105 billion. Born in France, he made his fortune in shipping and banking in the US. He left most of his money to charity.
18. Alexander Turney Stewart, worth $90 billion. Irishman who settled in the US in the early 19th century and made his fortune by starting the largest department store in New York, and running the first mail order business.
19. Henry Duke of Lancaster, worth $85.1 billion, another 14th century landed English nobleman.
20. Friedrich Weyerhauser, worth $80 billion. After making a fortune in timber, he built an enormous fortune by buying land in the US.
21. Jay Gould, worth $71 billion. He made his fortune on the railroad, as Vanderbilt's big rival. He was also known for speculation and cut-throat business practices.
22. Carlos Slim Helu, worth $68 billion, and the chairman and chief executive of Mexican telecoms firms Telmex and América Móvil. He is currently the richest man in the world.
He built an empire from very humble beginnings, building construction, mining and retail companies to form a vast conglomerate.
22. Stephen van Rensselaer, worth $68 billion, was an 18th century landowner, who benefited from owning the land on which Manhattan is now built.
23 Marshall Field, worth $66 billion. Retail and real estate mogul in Chigaco, and founder of University of Chicago with John D Rockefeller.
24 Sam Walton, worth $65 billion. The founder of Walmart.
25. Warren Buffett, worth $64 billion. Legendary long-term value investor. He has now begun giving away much of his incredible fortune to charity - and has pledged to give away half of his fortune in his lifetime.