[T]he
              extent of a poem may be made to bear mathematical relation
 to its merit — in other words, to the excitement or elevation —
              again in other words, to the degree of the true poetical 
effect which it is capable of inducing; for it is clear that the brevity
 must
              be in direct ratio of the intensity of the intended 
effect: — this, with one proviso — that a certain degree of duration is
              absolutely requisite for the production of any effect at 
all. 
            
Holding in view these considerations, as well as that degree of excitement which I deemed not above the popular, while
              not below the critical, taste, I reached at once what I conceived the proper length for my intended poem — a length of
              about one hundred lines. It is, in fact, a hundred and eight. 
My next thought concerned the choice of an impression, or effect, to be conveyed: and here I may as well observe that,
              throughout the construction, I kept steadily in view the design of rendering the work 
universally
 appreciable. I should be
              carried too far out of my immediate topic were I to 
demonstrate a point upon which I have repeatedly insisted, and which, 
with the
              poetical, stands not in the slightest need of 
demonstration — the point, I mean, that Beauty is the sole legitimate 
province of
              the poem. A few words, however, in elucidation of my real 
meaning, which some of my friends have evinced a disposition to 
misrepresent.
              That pleasure which is at once the most intense, the most 
elevating, and the most pure, is, I believe, found in the contemplation 
of the
              beautiful. When, indeed, men speak of Beauty, they mean, 
precisely, not a quality, as is supposed, but an effect — they refer, in
              short, just to that intense and pure elevation of 
soul — not of intellect, or of heart — upon which I have commented,
              and which is experienced in consequence of contemplating “the beautiful."
...
I have often thought how interesting a magazine paper might be written 
by any author who would — that is to say,
              who could — detail, step by step, the processes by which 
any one of his compositions attained its ultimate point of completion.
              Why such  a paper has never been given 
to the world, I am much at a loss to say — but, perhaps, the autorial
              vanity has had more to do with the omission than any one 
other cause. Most writers — poets in especial — prefer having it
              understood that they compose by a species of fine frenzy —
 an ecstatic intuition — and would positively shudder at letting
              the public take a peep behind the scenes, at the elaborate
 and vacillating crudities of thought — at the true purposes seized only
              at the last moment — at the innumerable glimpses of idea 
that arrived not at the maturity of full view — at the fully
              matured fancies discarded in despair as unmanageable — at 
the cautious selections and rejections — at the painful erasures
              and interpolations — in a word, at the wheels and pinions —
 the tackle for scene-shifting — the step-ladders and
              demon-traps — the cock’s feathers, the red paint and the 
black patches, which, in ninety-nine cases out of the hundred,
              constitute the properties of the literary 
histrio.