एतेन मंत्रराजेन सर्वोपनिषदात्मना । लेभिरे मुनयः सर्वे परं ब्रह्म निरामयम्
etena maṃtrarājena sarvopaniṣadātmanā | lebhire munayaḥ sarve paraṃ brahma nirāmayam
By this king of mantras—whose essence is all the Upaniṣads—all sages attained the supreme Brahman, free from every affliction.
Deductive attribution: Purāṇic narrator in Brahmottara-khaṇḍa (likely Sūta/compilational voice)
Scene: Sages in meditation; above them, a crown-like mantra (mantra-rāja) radiates, and Upaniṣadic mahāvākyas appear as streams merging into a single luminous Brahman-light, free of blemish.
The Śiva-mantra is equated with Upaniṣadic wisdom and is said to lead to realization of the supreme Brahman.
No tīrtha is mentioned; the emphasis is on mantra as a direct spiritual means.
Reliance on (and practice of) the mantra—especially japa—as the means to the highest attainment.