For blank verse is but a restricted prose, because there is as often as not no natural pause at the end of the line, and because other feet may be substituted for the iambus.
"The Literature of Ecstasy"
Albert Mordell
Where ye see one to be a trocheus another the iambus, and so entermingled not by election but by constraint of their seuerall accents, which ought not to be altred, yet comes it to passe that many times ye must of necessitie alter the accent of a sillable, and put him from his naturall place, and then one sillable, of a word polysillable, or one word monosillable, will abide to be made sometimes long, sometimes short, as in this quadreyne of ours playd in a mery moode.
"The Arte of English Poesie"
George Puttenham
At one moment the ten syllables are only to be made out by a Chaucerian lengthening of the mute e; at another the writer seems to be emulating Wyatt in altering the accent of syllables, and coolly making the final iambus of a line out of such a word as "answer."
"A History of English Literature Elizabethan Literature"
George Saintsbury