One of the oldest angle measuring devices – a kamal is most effective when measuring small angles (such as yesterday’s Tip of the day – 6 degrees). For a Kamal to measure a 6-degree angle, Drill a small hole in the centre of a 6cm x 6cm piece of hardwood. Tie a stopper knot in a piece of string and thread it through the hole. Mark the string 57cm from the board and hold that mark at your mouth, extending the board towards the horizon until the string is taut. The board will now cover 6 degrees.
More advanced versions can be found at http://kaloujm.com/page_kamal_uk.php