The Collaborative International Dictionary of English v.0.48:

Nighly \Nigh"ly\, adv.
   In a near relation in place, time, degree, etc.; within a
   little; almost. [Obs.]
   [1913 Webster]

         A cube and a sphere . . . nighly of the same bigness.
                                                  --Locke.
   [1913 Webster]