John Steele Gordon relates an interesting tale in Barron’s about the man who might have been the richest in human history.

One of the most intractable problems in economic history is translating the value of money over time. What would $1 million in, say, 1816, be worth in today’s money?

The consumer-price index, based on the price of a basket of commodities, works as a measure of inflation over small periods of time. But while the CPI has actually been calculated back to the beginning of the 19th century, such a period has seen the creation of a completely new and vastly richer economy.

The basket of commodities that people actually buy has changed radically. Servants were cheap in 1816; lunch could be bought for a nickel; the rent on a luxurious town house in Manhattan would have been under $100 a month. But clothes, which had to be handmade, were very expensive, as was private transportation (hence the phrase “carriage trade”).

The best we can do is to ballpark it: In 1816, $1 million would have made its owner one of the richest people in the country, easily in the top 10 of the Forbes 400 list, had there been one then. Indeed, a net worth of $1 million (or one million pounds sterling) was so rare in 1816 that the word millionaire had only just entered the English language.

So if grasping the economic meaning of $1 million a mere two centuries ago is difficult, how can we understand the wealth of a man who lived in the 14th century? One way is to see how his spending affected an entire national economy.

Musa Keita I (circa 1280 to circa 1337) was the ruler of the Mali Empire in west Africa. Taxing the many camel caravans that crisscrossed the Sahara Desert every year produced considerable imperial income. But two local commodities had made his country very, very rich: gold and salt. …

… WHILE IN CAIRO, THE EMPEROR and his vast entourage spent gold so lavishly on slave girls, clothes, food, and artwork that he flooded the Egyptian economy with the stuff, causing its price to fall by as much as 25%—an inflation in the same degree in prices in the Egyptian economy, one of the Muslim world’s largest and most prosperous.

Although Mansa Musa took out a substantial loan in gold on his way back from Mecca, perhaps to reduce the quantity in circulation and stem the inflation he had caused, the contemporary chronicles say that it was 20 years before the Egyptian economy fully recovered.