The Lotus Position (or padmasana) is a posture in Yoga, also used in Buddhist Meditation. It consists in sitting cross-legged with each foot placed atop the opposite thigh and the hands resting on the knees.
The purpose of the Lotus Position, or any other form used for meditation, is to be uncomfortable enough to prevent the person meditating from falling asleep, without being so uncomfortable as to be distracting.
Like other such positions, (reverse namaste is more or less its counterpart with hands), it's easy to do with joints in a good state and fully relaxed muscles, but otherwise attempts to assume it tend to be painfully straining. So, while the proper position is "the feet firmly atop the thighs", a frequent replacement and many depictions have the feet crossed before or underneath the legs. The pose with one foot on top of the opposite leg and the other on bottom is a "half lotus pose" (ardha padmasana); both feet on the bottom is "easy pose" or sukhasana, also commonly called "tailor style" or "Indian style".
