How do we know what accents people spoke with before the invention of recorded sound?

Question

Most movies and shows set in the past e.g. 1700s, 1600s etc will include some sort of accent. How do we know if people actually spoke in those accents?

Edit: this came up is because I was watching the CBS show Ghosts. In it, there are two ghosts from the American Revolution. The British Revolutionary and the American Revolutionary have distinctly different accents and it made me question how we actually know what they sounded like.

In: 8

Answer 1

Fun Fact: The British and American revolutionaries *should* sound basically the same, they should both sound basically American. The British didn’t develop the accent we think of as the standard British accent until after the American revolution. The modern American accent is much closer to how the British sounded at the time.