everything we've been taught about meter in poetry is wrong. . . sigh.

From Hugh's Prosody class:

Syllable-stress verse requires a fixed number of beats per line—just like stress-meter verse—but it also requires a fixed number of syllables per line (there are exceptions to both these rules, of course, but in principle this is the "normal" case).

-->Indeed, people who have been poorly taught poetic meter will often attempt to identify verse forms by the number of syllables (as in "this is in iambic pentameter; it has ten syllables per line").

Of course, we all now know why that statement makes no sense—a four-beat line of stress-meter verse can easily have anywhere from four to twelve syllables—or more.