At the time of the Mary Rose a nautical mile was reckoned to be about 5,000 feet. (Today it is set at 6,080 feet).

Because speed was measured with the log reel, nautical miles travelled per hour are called knots.

We say a ship travels at 9 knots, never 9 knots per hour!

In the picture you can see the "chip" in the water. The man in the background is measuring the time with his sandglass.