The banknote's inventor was sentenced to death

Seventeenth-century Sweden was the great copper power, so it decided to mint its currency in copper. Since copper was worth far less than silver, the coins had to be enormous: the biggest, plates of nearly 20 kilos, remain the heaviest coins in history. Going shopping was literally heavy lifting.

In 1661, the Bank of Stockholm, founded by Johan Palmstruch, offered the solution: leave your plates at the bank and walk away with a paper that represents them. Europe's first banknotes were born, and they were an instant hit.

Too much of a hit. Palmstruch printed far more notes than there was copper in the vaults, people came to redeem them, and the bank collapsed in 1668. He was sentenced to death — later commuted to prison. From the ashes of his bank rose Sweden's Riksbank: the oldest central bank in the world.