Yeah, I always thought a baritone guitar's tuning was exactly like a regular standard tuned guitar, just all 6 strings down perfect 4th, echoing others already typing here. Same exact pitches if you put a capo across your 7th fret, only sounding an octave lower.
First song I recall hearing that used "standard tuning, down a perfect 4th" was Type-O-Negative's "Christian Woman" in the very early 1990s. I believe this was just a regular slack-tuned guitar, not a a baritone, FWIW.
Other ways to get a low B, for what it's worth:
King's X tuning (on some songs): B-F#-D-G-B-E (strings 5-6, like drop-D, then both down a minor 3rd); top four strings are standard tuning, so soloing is not a crazy.
Slipknot and others use Drop-D (D-A-D-G-B-E), then all six strings down a minor 3rd (a "slack" version of Drop-D tuning): B-F#-B-E-G#-D
Or a standard 7-string, which has a low B (B-E-A-D-G-B-E); Korn tunes all 7 down one whole-step, to get a low A....
Zakk Wylde tunes his bottom string to A (of a 6 string) at times, and keeps everything else the same for solos in BLS...
Anyways, for what it's worth (and since you asked), I wrote a very small tuning book... over 10 years ago... It has some cool stuff in it, with some open, slack, dropped, and altered tunings. It's a real basic book though--more about staying "in tune," tuning on the gig, dealing with floating bridges, a discussion on equal temperament, and other stuff (not specifically about "tunings")
Amazon.com: Ultimate Guitar Tuning Pack (9780793590858): Dale Turner: Books
Dale