Garudapurana 1.39.6

1.39.6

mudrāyā darśanaṃ rudra mūlamantreṇa vā hara /
tejorūpaṃ raktavarṇaṃ sitapadmopari sthitam /
ekacakrarathārūḍhaṃ dvibāhuṃ dhṛtapaṅkajam //

One should show the mudrā, O Rudra, or [do so] with the root mantra, O Hara:
[meditating on him] whose form is radiance, red in color, seated upon a white lotus,
mounted on a one-wheeled chariot, two-armed, holding lotuses.