Here is a description of the aṣṭāṅga-yoga system, to which Dhruva Mahārāja was already accustomed. Aṣṭāṅga-yoga was never meant to be practiced in a fashionable city. Dhruva Mahārāja went to Badarikāśrama, and in a solitary place, alone, he practiced yoga. He concentrated his mind on the arcā-vigraha, the worshipable Deity of the Lord, which exactly represents the Supreme Lord, and thus thinking constantly of that Deity, he became absorbed in trance. Worship of the arcā-vigraha is not idol worship. The arcā-vigraha is an incarnation of the Lord in a form appreciable by a devotee. Therefore devotees engage in the temple in the service of the Lord as arcā-vigraha, a form made of sthūla (material) objects such as stone, metal, wood, jewels or paint. All of these are called sthūla, or physical representations. Since the devotees follow the regulative principles of worship, even though the Lord is there in His physical form He is nondifferent from His original, spiritual form. Thus the devotee gets the benefit of achieving the ultimate goal of life, that is to say, becoming always absorbed in thought of the Lord. This incessant thought of the Lord, as prescribed in the Bhagavad-gītā, makes one the topmost yogī.