Can You Solve This Incredibly Tricky Counterfeit Riddle?

Shelby Rogers

This riddle from TED-Ed managed to garner over 1 million views. Can you solve it before time runs out? Here's the scenario:

As the world's greatest mathematician, you've been imprisoned by an evil king. After years in jail, the king brings you before him enraged. He suspects one of his 12 governors paid taxes with a counterfeit coin. He says if you can determine the fake, you get your freedom. All 12 coins look identical. You can use the king's scale only three times and it's the only unit of measurement you have. You can write on the coins with your trusty marker, and that doesn't change its weight.