[Discussing the word dis-eate in Macbeth, amended by various editors to disseat, disease, disseizes and defeat. ]
. . . you may say that Shakespeare actually intended, by putting down something a little removed from any of the approximate homonyms, to set the reader groping about their network. One must consider, before dismissing this second idea as absurd, that the Elizabethans minded very little about spelling and punctuation; that this must have given them an attitude to the written page entirely different from ours (the reader must continually have been left to grope for the right word); that from the comparative slowness, of reading as of speaking, that this entailed, he was prepared to assimilate words with a completeness which is now lost; that only our snobbish ability of spelling imposes on us the notion that one mechanical word, to be snapped up by the eye, must have been intended; . . .
From Seven Types of Ambiguity by William Empson.
I'm trying to figure out the structure and meaning of the bolded part of this sentence.