Various, Notes and Queries, Vol. IV, Number 107…
“ Now Shakspeare was too good a sailor to suppose that a ship could be visible to a man on the surface [380] of the water a distance of fifteen miles; but at one-third of that distance it might be so. Therefore it would be necessary to take league as synonymous with mile in this instance, even if it were not corroborated by the necessity for a similar understanding in other places.But wherever Shakspeare uses the word league, its equivalence with mile is not only consistent with the sense, but, in some cases, absolutely necessary to it. ”
