大毘盧遮那成佛神變加持經 (Shubhakarasimha & Yixing 724) 7.128

7.128

Having made offerings endowed with the Dharma in this way, give rise to the mind of benefiting inexhaustible sentient beings;
Bowing the head to the Buddhas, holy devas, and others, abide on the corresponding seat and enter samādhi.
The rituals of the four dhyānas can cause joy and bliss to arise in the inner mind;
Through empowerment with ultimate truth, the mantra will attain samāhita.
When engaging in mantra recitation, I will now next explain its upāya:
The wise one, as previously revealed, visualizes the iṣṭadevatā directly in front,
And in the round, bright moon of their own heart, clearly sees the mantra syllables.
Then one should sequentially uphold them until the mind is pure and undefiled,
With the counts, time divisions, and appearance of signs fully satisfied according to the sūtra teachings.
Aiming to seek benefits endowed with characteristics, mantra siddhi will be accomplished as desired;
This is called worldly practice endowed with characteristics; the gates of four-limbed dhyāna are furthermore distinct.
The practitioner should generate a resolute mind, first contemplating the iṣṭadevatā on a single object,
Holding that deity's mantra and secret mudrā, and personally form the yoga image of the iṣṭadevatā;
As for the bodily forms, deportment, and the like, my body is non-dual and identical in conduct;
By abiding in the corresponding body of the fundamental ground, even one of little merit will attain accomplishment.
In the Chapter on the Supreme Meaning of Yoga, it says that one should next transform the vidyā syllable-door,
And visualize it to form the body of the iṣṭadevatā, until one sees the emblem of the body's secret.
The sūtra briefly teaches two forms: the visualization of the Samyaksaṃbuddha is foremost,
Next is the visualization of the Bodhisattvas and holy devas, with Mañjuśrī as the foremost;
Also according to the rank of that vehicle, one rotates with the corresponding mudrā and mantra.