If you are looking for poetry by either Emerson or Thoreau which depicts examples of why their texts are considered Transcendental, you may want to look at the following poems (both poets were always looking for beauty in both nature and the spirit of the individual). The following exemplify these ideals.
"Celestial Love" by Emerson and Waldon by Thoreau (specifically the chapters titled "Brute Neighbors,” “Sounds,” and “Solitude").
Outside of these examples, if you are looking for a primary source which describes very critical and specific aspects of both Emerson's and Thoreau's writings as being ones characteristic of the Transcendental movement, you can examine the link which follows this post. The article, written by Levi Asher, states the following:
Socially, the Transcendentalists stood for equality of women and innovation in the educational system. Philosophically they inclined towards a Platonic sense of idealism. In terms of literature and art, they were sympathetic towards the same styles the Romantic writers of England were experimenting with.
Perhaps the best primary source to examine is "The Dial: A Magazine for Literature, Philosophy, and Religion." This magazine is mentioned in Asher's article and many others which discuss the Transcendental movement, Emerson, and Thoreau.