The Collaborative International Dictionary of English v.0.48:

Toilsome \Toil"some\ (toil"s[u^]m), a.
   Attended with toil, or fatigue and pain; laborious;
   wearisome; as, toilsome work.
   [1913 Webster]

         What can be toilsome in these pleasant walks? --Milton.
   [1913 Webster] -- Toil"some*ly, adv. -- Toil"some*ness,
   n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

toilsomeness
    n 1: the quality of requiring extended effort [syn:
         laboriousness, operoseness, toilsomeness]