The Collaborative International Dictionary of English v.0.48:

Pore \Pore\, v. i. [imp. & p. p. Pored; p. pr. & vb. n.
   Poring.] [OE. poren, of uncertain origin; cf. D. porren to
   poke, thrust, Gael. purr.]
   To look or gaze steadily in reading or studying; to fix the
   attention; to be absorbed; -- often with on or upon, and now
   usually with over."Painfully to pore upon a book." --Shak.
   [1913 Webster]

         The eye grows weary with poring perpetually on the same
         thing.                                   --Dryden.
   [1913 Webster]