Convert from digit to league [nautical]

Unit Definition (digit)
The digit is a historic unit of distance equal to the width of a person's finger. Used in all the ancient civilizations of the Middle East and Mediterranean, the digit was equal to 0.75 inch or 19 millimeters with only the smallest variations. Typically, there were 4 digits in a palm, 16 in a foot, and 24 (sometimes 28) in a cubit. The word digit is from the Latin word for a finger or toe, digitus.

Unit Definition (league [nautical])
The nautical league is approximately equal to three nautical miles, 1/20 degree, or 5556 meters (metres). Note that it is not equivalent to the portugese, french and spanish measurements of the league. The nautical league is also different from the league defined on land.