In Scott's "Ivanhoe" the villain is a member of the Templars. an Order of crusaders, whose banner is called the
"Beau Séant". Despite extended search, I have been unable to find the meaning of the motto. I did find a couple ridiculous ones, such as "Looking nice".
I challenge the members to find what I could not.
(Throwing down my gauntlet of mail.)

Beau Séant - Be Glorious!

Dear tsuwm: sounds more appropriate than most of the ones I saw. However, can you give us a bit of explication?
This has to be medieval French. I don't see any imperative verb in "séant" . One of the banners I saw had two knights on one horse. I wouldn't call that "sitting pretty". And many of the sites I saw associated the motto with the eight pointed cross. How does the motto fit that?
The text I read had student notes, but I didn't feel like joining the club, so I saw only the notes included with the text at:
http://pd.sparknotes.com/lit/ivanhoe/section4.html

Whoa--no luck yet on séant, but look what I found during the search--check out the last def.:
season - 13c., from O.Fr. saison "a sowing, planting," from L. sationem (nom. satio) "a sowing," from pp. stem of serere "to sow" (see sow). Sense shifted in V.L. from "act of sowing" to "time of sowing." The verb meaning "improve the flavor of by adding spices" is c.1390, from O.Fr. assaisoner "to ripen, season," on the notion of fruit becoming more palatable as it ripens. Applied to timber by 1540. In 16c., it also meant "to copulate with." Seasoning (n.) is from 1580.
http://www.etymonline.com/s3etym.htm

Okay, I've gotten this far: Seant, voyez Sied.

Seant, Habilis, Decens, Decorus.

Il est bien seant, Decet.

Cet habit t'est bien seant, Sedet tibi haec vestis. Quintilianus.

On to sied: Sied, voyez Seant.

Il luy sied bien à parler, Loquitur laute, Scite dicit, Eleganter loquitur.

Voyez si cet accoustrement me sied bien, Vide an ornatus hic me condecet.

Cest habit te sied bien, Sedet tibi haec vestis.
I'm not even going to try and translate; hopefully the...Latin?...will help somebody else do it. Both quotes came from
http://humanities.uchicago.edu/forms_unrest/TLF.html#form, a French dictionary from 1606. Oh--I went to sied because voyez means see.

A séance is a sitting. So "beau séant" could mean "They ride well", or maybe "They ride bravely".
séance
n.
5Fr, lit., a sitting < seoir < L sedere, to SIT6 a meeting or session; now specif., a meeting at which a medium seeks or professes to communicate with the spirits of the dead

they ride well

It certainly does sound like 3rd person plural. Might could get translated in the infinitive.

The site I found, a (commercial) history of the Knights Templar, offers tsuwm's "Be glorious (noble)!" as one possible meaning of the banner's name, but they're not sure, either:

The word beau is now generally conceived to mean beautiful, but it means much more than that. In medieval French it meant a lofty state, for which translators have offered such terms as "noble,""glorious," and even "magnificent." As a battle cry then, "Beau Seant" was a charge to "Be noble" or "Be Glorious."

...Other etymological suggestions include piebald, which is perhaps closer to the mark. Piebald means spotted or two color as in a piebald horse or cat. This certainly fits the description of the Beauséant, for it consisted of a black square above a white one.


http://templarhistory.com/beauseant.html