In the process of worshiping the Deity it is sometimes enjoined that one worship the Deity within the mind. In the Padma Purāṇa, Uttara-khaṇḍa, it is said, “All persons can generally worship within the mind.” The Gautamīya Tantra states, “For a sannyāsī who has no home, worship of the Deity within the mind is recommended.” In the Nārada-pañcarātra it is stated by Lord Nārāyaṇa that worship of the Deity within the mind is called mānasa-pūjā, One can become free from the four miseries by this method. Sometimes worship from the mind can be independently executed. According to the instruction of Avirhotra Muni, one of the nava-yogendras, as mentioned in Śrīmad-Bhāgavatam, one may worship the Deity by chanting all the mantras. Eight kinds of Deities are mentioned in the śāstra, and the mental Deity is one of them. In this regard, the following description is given in the Brahma-vaivarta Purāṇa.
In the city of Pratiṣṭhāna-pura, long ago, there resided a brāhmaṇa who was poverty-stricken but innocent and not dissatisfied. One day he heard a discourse in an assembly of brāhmaṇas concerning how to worship the Deity in the temple. In that meeting, he also heard that the Deity may be worshiped within the mind. After this incident, the brāhmaṇa, having bathed in the Godāvarī River, began mentally worshiping the Deity. He would wash the temple within his mind, and then in his imagination he would bring water from all the sacred rivers in golden and silver waterpots. He collected all kinds of valuable paraphernalia for worship, and he worshiped the Deity very gorgeously, beginning from bathing the Deity and ending with offering ārati. Thus he felt great happiness. After many years had passed in this way, one day within his mind he cooked nice sweet rice with ghee to worship the Deity. He placed the sweet rice on a golden dish and offered it to Lord Kṛṣṇa, but he felt that the sweet rice was very hot, and therefore he touched it with his finger. He immediately felt that his finger had been burned by the hot sweet rice, and thus he began to lament. While the brāhmaṇa was in pain, Lord Viṣṇu in Vaikuṇṭha began smiling, and the goddess of fortune inquired from the Lord why He was smiling. Lord Viṣṇu then ordered His associates to bring the brāhmaṇa to Vaikuṇṭha. Thus the brāhmaṇa attained the liberation of sāmīpya, the facility of living near the Supreme Personality of Godhead.