Source : Webster's Revised Unabridged Dictionary (1913)

Restful \Rest"ful\ (r?st"f?l), a.
   1. Being at rest; quiet. --Shak.

   2. Giving rest; freeing from toil, trouble, etc.

            Tired with all these, for restful death I cry.
                                                  --Shak.
      -- {Rest"ful*ly}, adv. -- {Rest"ful*ness}, n.

Source : WordNet®

restfulness
     n : the attribute of being restful; "he longed for the
         restfulness of home"