This is what I gathered from this John Kay piece in the FT: “The second richest man of all time was poorer than us”:
Nathan Rothschild was the richest man in the world when he died in 1836. A list compiled by Forbes magazine, ranks him as the second richest man who ever lived – ahead of John D Rockefeller, and way ahead of Mexican telecoms mogul Carlos Slim and Bill Gates of Microsoft. (The richest was a Roman general who was the power behind Julius Caesar’s throne.) The figures used by Forbes are, of course, adjusted for inflation.
But what does “adjusted for inflation” mean? Rothschild died of septicaemia following an abscess, and in spite of buying the best medical attention available in Europe at the time. He had never been in a car, a train or an aircraft, nor visited the Taj Mahal, heard recorded music, seen a film, made a phone call or used electric light. Nor (despite the legends about the killing he made from inside information) could he have heard about the outcome of Waterloo until many hours after the battle was won. And he was dead at the age of 58 from an illness that could today be cured by an antibiotic costing a few pence.