The Collaborative International Dictionary of English v.0.48:

Transcendentalist \Tran`scen*den"tal*ist\, n. [Cf. F.
   transcendantaliste.]
   One who believes in transcendentalism.
   [1913 Webster]

WordNet (r) 3.0 (2006):

transcendentalist
    n 1: advocate of transcendentalism

Moby Thesaurus II by Grady Ward, 1.0:

56 Moby Thesaurus words for "transcendentalist":
   Cyrenaic, Eleatic, Epicurean, Megarian, Stoic, adept, animist,
   animistic, anthroposophist, atomistic, cabalist, cosmotheistic,
   eclectic, empirical, esoteric, eudaemonistic, existential, hedonic,
   hedonist, hedonistic, humanist, humanistic, idealistic,
   instrumentalist, mahatma, materialistic, mechanistic, metaphysical,
   monistic, mystagogue, mystic, naturalistic, nominalist,
   panlogistical, pantheistic, positivist, positivistic, pragmatic,
   pragmatist, rationalistic, realist, realistic, scholastic,
   sensationalistic, supernaturalist, syncretistic, theistic,
   theosophist, transcendentalistic, utilitarian, vitalistic,
   voluntarist, voluntaristic, yogi, yogin, yogist