Another aspect of multum in parvo I've noticed is that the smaller and more circumscribed by rules the form, the shorter the fuse. Haiku composition, so tranquil in intent, is in its English and American practice at least a landscape of Kurosawa-like mayhem. An insistence on 17 syllables or an acceptance that the difference syllabic structures of English can reasonably lead to fewer or more beats, a prescription of the necessity of season-words from approved lists or a looser vignette-writing without benefit of cherry trees - these and all stylistic points between have their partisans and hostiles. Exchanges on online lists - I used to belong to one - lead to many a list member getting the hump and their coats.
Yannis Ritsos wrote some memorable one-line poems - monochords - which I've been re-reading. At their best, these conjure up a whole mood, a narrative, from 9 or 10 words. I wonder what would happen, though, if every started writing them, and tried to excavate from Ritsos' practice a set of rules... Internet flaming agogo, I suspect.
And then, like the Invisible Shrinking Man, how small can you go? Concrete poetry got down to very few words indeed - a sentence, a phrase, a word. Ian Hamilton Finlay's garden at Little Sparta - and his paper output - works through context and juxtaposition and even typography - those and the prior knowledge of the viewer. Perhaps one of the impulses or tendencies of poetry, which cherishes language and its smallest components, is to use a single word in a way it has never been used before, with everything else a kind of advanced mark-up language.