Parasang

The parasang is a historical Iranian unit of itinerant distance, the length of which varied according to terrain and speed of travel. The European equivalent is the league.
The parasang may have originally been some fraction of the distance an infantryman could march in some predefined period of time. Mid-5th-century BCE Herodotus (v.53) speaks of [an army] traveling the equivalent of five parasangs per day.