Both thinkers were drivers of the Transcendentalist movement. I think that there was a slight difference in how both perceived the ends of the movement, though. For Emerson, the transcendentalist position of revering nature, driving the idea of embracing individuality, and defying the idea of conformity are all extremely important for the individual to live a contented life. Emerson takes these points on a subjective level, seeking to broaden social change through individual embrace of such notions of the good. This can be seen in all of his works, but is present in his work entitled Nature:
The work is, as its title suggests, a study of Nature and humanity’s relationship to Nature. Part philosophical treatise, part prose poem, Nature attempts to outline the pathway to spiritual enlightenment, which begins with not only the praise and appreciation of Nature but also the belief that it is divine.
For Emerson, the path to true understanding and enlightenment is an individual one that embraces nature, individual, and the intrinsic uniqueness in both. This is a subjective experience and in praising the subjective, Emerson is traditionally Romantic in his idea that the universal stems from it.
Thoreau shares in much of the same, but he is a bit different in the take he proposes. Thoreau embaced the Transcendentalist ideas concerning the nature, the subjective individual, and striking a position of anti- conformity, but injected a political dimension into this discussion. While Emerson hoped for social change, Thoreau seemed to demand it. The politicization of Transcendentalism is more present with Thoreau, who argued that if one was committed to Transcendentalist ideas, then political dissent was inevitable:
In “Resistance to Civil Government,” Thoreau states, 'Unjust laws exist: shall we be content to obey them, or shall we endeavor to amend them, and obey them until we have succeeded, or shall we transgress them at once?' Thoreau’s answer was to transgress, and go to jail if necessary, for as he says, 'Under a government which imprisons any unjustly, the true place for a just man is also a prison.”
For Thoreau, the recognition of the Transcendentalist goals into political and social movements of change is of vital importance. Wihle Emerson embraces these notions of good on a personal leve, Thoreau argues that they are vitiated in their potency if not applied to the level of social and political forms of change and reform.