<BLOCKQUOTE><font size=“-1”>quote:</font><HR>I’ve always wondered exactly what the purpose of meditating in full-lotus is (as opposed to just Indian-style or even sitting in a chair)?
Might it be:
- To purposefully close off the lower channels so that all energy can be focused on opening the microcosmic orbit first?[/quote]
That’s true for Taoist and some of the more esoteric practices of Yogic meditation (Kundalini, Tantric, etc.). However, most Zen practitioners don’t really care about microcosmic orbits, etc…
<BLOCKQUOTE><font size=“-1”>quote:</font><HR>2) To develop better circulation in the legs thru such progressive training? [/quote]
Superior circulation in the legs is something one should achieve prior to sitting in full-lotus pose. If you don’t I can almost guarantee one or both of your feet will fall asleep during meditation. Blood flow is increased through several different leg and hip-flexor exercises (I prefer the Yoga exercises personally).
<BLOCKQUOTE><font size=“-1”>quote:</font><HR>3) To provide a stable base where the spine can more easily be maintained properly erect? [/quote]
Absolutely. Every meditative tradition which uses full-lotus primarily uses it for that reason. As mentioned above, sitting in “indian style” (called Easy pose in Hatha Yoga) and straightening your spine will cause an overwhelming feeling you’re about to fall backwards, and this can be very distracting. The trick is to get your knees down, which requires loose hip flexors. There are several exercises which help to loosen the hip-flexors (I’ve outlined some below) and get the knees down. In fact, until your knees come closer to the floor when you’re sitting cross legged, the full-lotus pose will be a near impossibility.
<BLOCKQUOTE><font size=“-1”>quote:</font><HR>4) To make your legs numb and increase your tolerance for pain![/quote]
LOL! Although there are probably some readers rubbing their jaws right now and thinking “yeah, that just might work…” 
To answer your question: no, there isn’t really any advantage (with the exception of the possible closing or stimulation of energy channels/chakras in Taoist or other meditations) to sitting in full-lotus over other sitting postures. In fact, sitting on the edge of a chair, bench, or stool is recommended to anyone too inflexible, thick in the legs, or suffering knee/ankle injuries for meditation. In this case, the spine still needs to be kept straight.
The straight spine is a figurative term, as the spine in its natural state is “S” curved and not a straight line. Essentially a “straight” spine is a comfortable and fully erect spine. It really relies on the shoulders for me. If my shoulders are held too high, I’ll feel pain in my lower back, if my shoulders are slouched, I’ll feel pain in my upper-to-mid back.
There are several good meditative postures. Standing, or Zhan Zhuang; kneeling, or sieza (I recommend tucking a pillow between your thighs and calves to alleviate pressure on the knees, or using a kneeling bench); sitting in a chair (you should sit at the edge of the chair to prevent leaning on the back rest); half-lotus which puts one knee on the floor; and/or full-lotus for the more flexible.
I personally use a Hatha Yoga posture called Perfect pose, which balances me nicely. To get into perfect pose, sit on your “sitting bones” (the end of the pelvis) with your legs open in front of you. Pull one foot up against the genitals/perenium, and set the other foot in front of it. This should put both knees on the ground.
If your hip-flexors are tight, and therefore your knees won’t touch the ground in any pose, try putting a cushion under your butt which will lift you above the plain of your knees. This way you can still meditate without the distraction of falling over.
I posted the following in another forum topic on lotus pose:
Here’s a basic lesson in sitting: Begin by sitting cross-legged on the floor. How far off the floor are your knees? How intense is the feeling of falling backward? Now straighten your legs out in front of you and open them as wide as you can. Put your hands behind you and sit forward with a little lift (this should put you at your maximum stretch). How wide can you get your legs?
If your knees sit higher than 2-3 inches off the floor, if you feel you are about to fall over constantly, and/or you can’t spread you legs wider than 45 degrees apart, you need to work your hip flexors. If not, just practice half Lotus with each leg for equal amounts of time (5-10 minutes) then pull your legs into full Lotus for 1-2 minutes. Work up from there.
To stretch your hip flexors, begin by sitting with your legs open and at their maximum stretch (as above). Reach out in front of you and stretch. Relax in the stretch, and gently work your way (your arms, chest, and head) down to the floor (don’t “bounce!”). When you’ve had enough of this, pick up a foot (bend the knee) and pull it to your chest. Don’t curve your back or lean your body toward your foot, bring your foot to it. Do this gently, and don’t stretch to the point of pain. Pay attention to your knee and ankle joints, if you feel pain there, back off the stretch a little until you’re comfortable. Set the foot down either on the thigh to loosen the ankles, or against the perineum (that tuft of skin between the sexual organs and the anus), and stretch out toward the extended leg. Straighten out the leg again, pick up the other foot, and repeat the above process of bringing your foot to your chest and stretching. Then straighten that leg, put your hands behind you and sit forward with a lift, and stretch forward again (you should be slightly closer to the floor than in the previous stretch). Finally, pull both feet together in front of your groin and gently bounce your knees up and down. The key word here is gently. If at any time you feel intense pain in one of these stretches, back off and relax the muscles. Once you’ve gotten your flexors stretched (daily practice for about six weeks) to the points mentioned above, you can then begin to work on half and full Lotus posture.
Without going outside, you may know the whole world.
Without looking through the window, you may see the ways of heaven.
The farther you go, the less you know.
–Lao Tsu
