on what nature is and can do in our own lives as well as what we must do in order to live our best lives.Henry David Thoreau lamented that "the mass of men lead lives of quiet desperation," suggesting that people work more than they have to in order to buy things that they don't need, that we resign ourselves to a life of too-much work and eventually give up the idea that we could live any differently. This, for him, is a terrible (and avoidable) tragedy. He also spent a night in jail for refusing to pay his poll tax, a tax levied on all citizens regardless of income, because he did not want his money to go to support the institution of slavery or an unjust war in Mexico. Transcendentalist literature often seeks to help its audience live better, more fulfilling, lives by advocating for simplicity, social justice, and self-reliance.

Transcendentalism is a movement that is located in American thought in the 19th Century.  It was one of the first literary and intellectual movements in America.  Of the many things that Transcendentalism means, the fundamental idea sought to inject emotions into daily life and paradigms of thought.  Essentially, the Transcendentalists saw life and consciousness as an exercise for emotions and emotional thought.  They wanted to bring more emotions into how human beings acted and thought.  In doing so, the movement asserted a couple of truths that ended up defining it.  The first was the call to individuality.  Transcendentalists were strong advocates of being an individual and breaking away from conformist society.  It is fromt the Transcendentalist thinkers that we get the idea of "walking to a different drummer" and "Know thyself."  These notions develop the idea that doing what society says might not be the best course of action.  Transcendentalism ended up becoming strongly associated and almost defined by this call to individuality and the zealous defense of it.

The previous thoughts were quite strong.  I would only add that Transcendentalism seems to be the Americanized version of the European Romantic movement with its emphasis on subjectivity and emotions.  The transcendentalist thinkers really strove to place a primacy on the subjective experience as being distinct from all else.  When Whitman writes “Song of Myself,” it’s Transcendental, in part, because he is not kidding around.  He literally believes that the subjective experience is something that has universal application.  Through the subjective, one can understand the objective. This emphasis on the emotional frame of reference to consciousness was powerful given the rapid growth of industrialization and the growing collective conformity that accompanied it in early America.  The meaning of Transcendentalism in such a context brings to light how the modern definition of America was set against opposing polarities that sought to bring form and meaning to a nation that was nebulous and responsive to different forces of change.

Transcendentalism was a style of writing that emerged from the Romantic style of writing, around 1840.  Just like music has different styles that are popular at different times, writing too has different styles throughout  history.  In America, the transcendentalists were motivated and inspired by nature, individualism (belief and celebration of oneself), a belief in universal truth that transcended (or went beyond) our mortal existences and a focus on the dignity of manual labor and personal introspection.  In their writing, they focused on identifying truths of human nature, and finding great joy and wisdom in those truths, revering them as sacred and spiritual.  They delighted in nature, and often found nature itself to be very spiritual and a conveyor  of truth and beauty.  They also focused on how every person should trust themselves, and should rejoice in all of their own beauty, instead of relying on others or the world to form their opinions or ideas.

The most famous transcendentalists are Ralph Waldo Emerson, who wrote numerous essays, the most well-known being "Self-Reliance," where he preached the importance of relying one yourself as a source of truth and wisdom.  Then, Henry David Thoreau, who wrote Walden, a book on how he went to live by himself on Walden Pond, reaping truth and satisfaction from the work of his own hands.

I hope that those thoughts helped; good luck!

There is more than one definition of the literary movement of 1836 to 1846 of several New England writers known by that name.  It was essentially a religious-spiritual movement expressed in poetry and prose:

Transcendentalism began as a religious concept rooted in the ideas of American democracy. When ... Ralph Waldo Emerson [,] decided that the Unitarian Church had become too conservative, they espoused a new religious philosophy, one which privileged the inherent wisdom in the human soul over church doctrine and law.  (enotes Summary)

and

...they may be defined in a somewhat wider perspective as children of the Puritan past who, having been emancipated by Unitarianism from New England's original Calvinism, found a new religious expression in forms derived from romantic (sic) literature and from the philosophical idealism of Germany (Miller iv).

Ralph Waldo Emerson, and the other main proponents of this philosophy (notably Henry David Thoreau, Margaret Fuller, William Ellery Channing, and Orestes Augustus Brownson) believed that the Unitarianism current in academic and intellectual circles at that time were becoming too much like the entrenched bureaucratic Christianties of Europe (such as Roman Catholicism and the Anglican Church) and less like the kind of religions on which much of New England was founded.  It must be remembered that one of the main sources of argument between the Church of England and the Puritans and other New World sects (although by no means the only point of contention) was the self-determination of the faithful's relationship with God.  This coincided with the American belief in democracy, and shunned religious hierarchies such as the ones coming into being in the Unitarianism of the time.  One of the most famous works of this movement's title supports this; the essay by Emerson entitled "Self-Reliance" explains most of Emerson's, and the movements, main tenets.  Essentially it is a religious belief that holds that every human being may find God within the "genius" of his own self; that "trusting thyself' is the most important virtue, and people that are truly self-reliant will find God and follow the right path.  Nonconformity should not frighten the faithful from trusting themselves, and everyone has the responsibility to think for themselves.  This is a simplification, of course, but Emerson is rejecting the ideas of a received knowledge from outside (such as from a church hierarchy) determining a person's faith in God; Emerson thought this essentially personal and only possible through self-realization.  Transcendentalists wrote poetry, too: Thoreau, for example, wrote early in his life of his struggle to find his true self and to relate to God.

I am a parcel of vain strivings tied
    By a chance bond together,
Dangling this way and that, their links
    Were made so loose and wide,
                     Methinks,
        For milder weather. ("Sic Vita" lines 1-6, Miller 231-2)

Not every transcendentalist was concerned with the same things; while Emerson may have been largely concerned with religion, and Thoreau with the self, Alcott commented on the two other authors, and Fuller wrote about women.  But these writers were joined in the spirit of American individualism, expressed mainly in religious terms.

Source: The American Transcendentalists: Their Prose and Poetry.  Perry Miller, ed.  Garden City, New York: Doubleay Anchor Books, 1957.