This seems like the right thread to add some info about zen meditation ("zazen") for those who are interested in trying it. These are some pages from an american zen master's website: how to sit zazen and stretches to get to the lotus position.

What I find interesting about zazen is that the emphasis is entirely on posture, with nothing that the practitioner is supposed to think or do, and this is said to have a "balancing" effect on the mind. Having tried it for about a week I can say that it does seem to induce a state of somewhat relaxed alertness, but that the effect varies widely depending on how you were feeling before you did the zazen. Also, it's extremely difficult to maintain motivation to do it every day as recommended, because of the boredom and discomfort of sitting in lotus, staring at the wall.

As to whether this has any applications to rationality, I'm unsure. According to practitioners it may help in avoiding being overcome by emotion, and increasing concentration, but these claims may be a dishonest attempt at proselytisation by buddhists ("join our religion and gain these benefits") and I'm having trouble tracking down any satisfactory references. If anyone else has any experience with this I'd be interested to hear about it.