Definition of "farsakh"

The next day was to take us to Anár, over a desert of twelve farsakhs, and it was here we might expect the robbers.

1846, Journal of the Royal Asiatic Society of Great Britain and Ireland, page 353

The old authors considered Demâvend the highest mountain in the world, and estimated its height at four to five farsaks

1888, Royal Geographical Society (Great Britain), Proceedings of the Royal Geographical Society and Monthly Record of Geography, page 86

From Rai to Damghan, 80 farsakhs; from Damghan to Nishapur, 80; total from Rai to Nishapur, 160 farsakhs.

1911, A.B. Wiliams Jackson, From Constantinople to the Home of Omar Khayyam, page 178