When you think of a coin, you'd probably think of a small round metal disc, with small denomination as face value.
But back in 17th century Sweden, coins called "platmynt" could actually be slabs of metal up to several inches thick, weighing as much as 43 pounds.
As you can imagine, lugging around heavy money wasn't convenient, so the platmynt actually led to the invention of the world's first banknote:
Illustrations of the era depict citizens with sacks of copper plates over their back or pulling a load of plates to the bank on a sled. This inconvenience was the catalyst for the creation of the world’s first bank notes. In the 1660’s, a bank was formed where plates could be deposited in return for a paper certificate of value. This paper money was an instrument which could be exchanged in commerce and the value repaid to the bearer in copper at the bank. This led to the creation of the world’s first central bank, Sveriges Riksbank (The National Bank of Sweden).