His rhapsodies are but rough notes—the stenographic memoranda of poems—memoranda which, because they were not all-sufficient for his own intelligence, he cared not to be at the trouble of writing out in full for mankind. In all his work we find no conception thoroughly wrought. For this reason he is the most fatiguing of poets. Yet he wearies in saying too little rather than too much. What, in him, seems the diffuseness of one idea, is the conglomerate concision of many: and this species of concision it is, which renders him obscure. With such a man, to imitate was out of the question. It would have served no purpose; for he spoke to his own spirit alone, which would have comprehended no alien tongue. Thus he was profoundly original. His quaintness arose from intuitive perception of that truth to which Bacon alone has given distinct utterance—“There is no exquisite Beauty which has not some strangeness in its proportions.” But whether obscure, original, or quaint, Shelley had no affectations. He was at all times sincere.
—Edgar Allan Poe, “Shelley and the Poetic Abandon,” The Unknown Poe (City Lights Books, 1980)