In the words of Ralph Waldo Emerson, in his 1842 lecture The Transcendentalist:
"The Transcendentalist adopts the whole connection of spiritual doctrine. He believes in miracle, in the perpetual openness of the human mind to new influx of light and power; he believes in inspiration, and in ecstasy. He wishes that the spiritual principle should be suffered to demonstrate itself to the end, in all possible applications to the state of man, without the admission of anything unspiritual; that is, anything positive, dogmatic, personal. Thus, the spiritual measure of inspiration is the depth of the thought, and never, who said it? And so he resists all attempts to palm other rules and measures on the spirit than its own....
"It is well known to most of my audience, that the Idealism of the present day acquired the name of Transcendental, from the use of that term by Immanuel Kant, of Konigsberg, who replied to the skeptical philosophy of Locke, which insisted that there was nothing in the intellect which was not previously in the experience of the senses, by showing that there was a very important class of ideas, or imperative forms, which did not come by experience, but through which experience was acquired; that these were intuitions of the mind itself; and he denominated them Transcendental forms. The extraordinary profoundness and precision of that man's thinking have given vogue to his nomenclature, in Europe and America, to that extent, that whatever belongs to the class of intuitive thought, is popularly called at the present day Transcendental...."
Ralph Waldo Emerson
The Transcendentalist, 1842