The Transcendentalist Movement, like all other movements, was a reaction to the unsettling feelings authors felt based upon the previous movements. The immediate movement previous to the Transcendental movement was Romanticism, which was a reaction to The Age of Reason. Given that the Romantic movement overlapped, and some of the Transcendentalists still upheld Romantic ideals, one could assume that the Transcendentalist movement was more of a secondary reaction to The Age of Reason over dislike with the Romantic period.
The Transcendentalist movement was popular between 1836 and 1846. This movement was influenced by Immanuel Kant. Kant believed that an individual needed to think autonomously and not rely upon dictates made by outside forces (people/ideas of "authority"). Therefore, his influence upon Transcendentalism came from the fact that the Transcendentalists believed that a man/woman was best when they were able to self-reliant and independent of oppression/forced ideologies.Basically, these writers believed in the inherent good nature of mankind.
Themes which were popular in the movement were ones which spoke to self-actualization, the impact of nature and the meaning which aligned with natural images, and social reform.
Transcendentalists tended to use free form in poetry given their desire to pull away from the constraints which formed poetry placed upon them. The tone of the Transcendentalists was one of the exalted. The writers were intense and their writings proved to be deeply meaningful.
Popular authors of the period were Ralph Waldo Emerson, Margaret Fuller, and Henry David Thoreau.