there's also another even tougher nianfo, circulating
Buddha 绕佛 meditation method in Avatamsaka sutra known as 般舟三昧
or 佛力三昧 practiced by 德云比丘(圆教处住 bodhisattva).
solely enclose for 90 days cannot sleep, cannot sit!
just keep on nianfo, while circulating the
Buddha 绕佛. but...can eat a little.
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