Shurangama Sutra, Volume 5: The Twenty-Five Sages' Methods of Perfect Penetration – Upanishad

Original Text: Upaniṣad, also known as Dust Analyst, immediately rose from his seat, prostrated at the Buddha's feet, and addressed the Buddha: "I too contemplated the Buddha’s initial enlightenment. Observing the impurity of form, I developed profound revulsion. I realized that the nature of all form arises from impurity—from unclean bones to subtle dust, eventually returning to emptiness. Both emptiness and form became non-existent, and I attained the state of non-learning. The Tathāgata confirmed me as 'Niṣada' (Subtle Dust). When the dust of form was exhausted, the subtle form containing profound secrets became perfectly pervasive. Through this contemplation of form, I attained Arhatship. When the Buddha inquired about perfect penetration, according to my realization, the contemplation of form as the fundamental cause is supreme."

Explanation: Upaniṣad immediately stood up from his seat, prostrated at the Buddha’s feet, and said to the Buddha: "After the Buddha’s initial enlightenment and his teachings to the bhikṣus, I chose to practice the contemplation of skeletons. Observing the impurity of the physical body, I developed deep revulsion toward it. I realized that the nature of all form originates from impurity—the form of unclean bones transforms into subtle dust, gradually returning to emptiness. I realized both emptiness and form are non-existent, attaining the fourth fruition of non-learning. The Tathāgata confirmed me as 'Niṣada' (Subtle Dust). Ultimately, when the perception of form within the six dusts (sense objects) was exhausted, the subtle form contained profound and secret truths. Through this realization regarding form, I attained Arhatship. When the Buddha inquired about perfect penetration, according to my realization, the contemplation of the body’s impurity is the most fundamental."

Upaniṣad practiced the contemplation of skeletons, observing the impurity of the physical body. He visualized the body as bones, then further refined the bones into subtle particles of dust. Finally, the subtle dust vanished, becoming emptiness. All these contemplations occurred within profound meditative concentration. The visualized bones belong to 'concentrated karma-produced form' (定果色), imperceptible to others; only he could perceive them with the wisdom-eye in samādhi. This perception was not with the physical eye, otherwise others would also see it. After perceiving the bones in samādhi, he continued his contemplation, refining the bones into the subtlest particles approaching the emptiness of space, ultimately transforming them into nothingness. Within his mind, both form and emptiness ceased to exist; all became empty. These states belong to concentrated karma-produced form, arising from samādhi. With both concentration and wisdom, through such samādhi, one can liberate from the three realms.

Without meditative concentration, attempting to contemplate these principles can only involve mental imagination. One can never truly visualize bones or subtle dust, much less transform dust into emptiness and then empty that emptiness itself. Therefore, the balanced cultivation of concentration and wisdom is called genuine practice, and its result is genuine realization. The cultivation and realization of all dharmas follow this principle; there are no shortcuts, and there is no bypassing the cultivation of concentration.