The Collaborative International Dictionary of English v.0.48:

Purposely \Pur"pose*ly\, adv.
   With purpose or design; intentionally; with predetermination;
   designedly.
   [1913 Webster]

         In composing this discourse, I purposely declined all
         offensive and displeasing truths.        --Atterbury.
   [1913 Webster]

         So much they scorn the crowd, that if the throng
         By chance go right, they purposely go wrong. --Pope.
   [1913 Webster]

WordNet (r) 3.0 (2006):

purposely
    adv 1: with intention; in an intentional manner; "he used that
           word intentionally"; "I did this by choice" [syn:
           intentionally, deliberately, designedly, on
           purpose, purposely, advisedly, by choice, by
           design] [ant: accidentally, by chance,
           circumstantially, unexpectedly, unintentionally]