Whilst dodging apples, Sir Isaac Newton had a few other good ideas in his career. The second one that we see in our daily lives is the small ridges along the edge of coins. These days they only serve in identifying coins by feel, but originally they prevented thievery!
For the first few thousand years of currency, coins were actually worth the value they represented. A ten dollar gold coin was manufactured with ten dollars worth of gold. So when you sold a cow, you would be making a legitimate trade for something of equal value. (and easier to carry in your pocket) Some less than honest people had the bright idea to take advantage of the crudely made coins. Any time they got their hands on a gold or silver coin, they would shave a little bit of the precious metal from the coin. It wouldn’t be enough to notice any difference in size or weight, so the next person accepted the token as being worth the usual ten bucks, but over time the thief would collect up a pile of free money.
So our buddy Isaac (I would presume sometime around 1700… ie: his lifetime) came up with the clever solution of manufacturing coins with fine ridges along the edge. That way, it would be instantly noticeable if somebody attempted to shave off some metal. Of course modern coins, as of the last 100 years or so, have little true value in the metal used, but the ridges stuck around, and are much appreciated by blind people to tell a penny from a dime.
Bonus fact: the movie cliche of biting a gold coin is not to verify it’s real gold. Gold coins are tooth-breakingly hard. The practice was to check for another nasty gold-thieving technique of hollowing out coins. If a coin collapsed when bit, you knew it had been emptied of it’s core values.