The Collaborative International Dictionary of English v.0.48:

Cogitate \Cog"i*tate\, v. i. [imp. & p. p. Cogitated; p. pr. &
   vb. n. Cogitating.] [L. cogitatus, p. p. of cogitare to
   reflect upon, prob. fr. co- + the root of aio I say; hence,
   prop., to discuss with one's self. Cf. Adage.]
   To engage in continuous thought; to think.
   [1913 Webster]

         He that calleth a thing into his mind, whether by
         impression or recordation, cogitateth and considereth,
         and he that employeth the faculty of his fancy also
         cogitateth.                              --Bacon.
   [1913 Webster]