For over two millennia, many East Asian countries used a type of coin known as “cash” (not to be confused with ready money). It was a round coin with a distinctive square hole, cast in various metals depending on the time, place, and value. This archaeological site in Chichibu tells the story of cash and mining in Japanese history.
The first cash was minted in China during the Warring States period, around 475–221 B.C. As the subsequent coinage circulated around the empire and beyond, its shape became the basis for money across Asia. Imitations were issued far and wide, from Sogdiana to the Malay Archipelago, not to mention Vietnam, Korea, and Japan.
About the source: Atlas Obscura
Atlas Obscura aims 'to inspire wonder and curiosity about the incredible world we all share'. You can contribute to their collection on their website.