Srimad Bhagvata Mahapurana: Book 4: Chapter 8: Verses 74-82
He spent the third month waiting upon the glorious Lord through Samadhi (abstract meditation), taking water (alone) every ninth day. Having (fully) controlled his breath, he fixed his mind and meditated on the (Supreme) Divinity during the fourth month too, inhaling the air every twelfth day. When the fifth month commenced, the prince stood motionless like a post on one foot, contemplating on Brahma (the Absolute) with his breath fully controlled. Withdrawing his mind, the substratum of the senses and their objects, from all other objects, he fixed it on the form of the Lord enthroned in the heart and perceived nothing else. All the three worlds (the earth, heaven and the intermediate region) began to shake as he meditated on Brahma (the Supreme), the ground of Mahat-tattva (the principle of cosmic intelligence) and the other categories, the Ruler of both Pradhana (matter) and Purusa (the spirit). When the prince (Dhruva) stood on one foot, the earth, pressed by his great toe, leaned to one side at that spot, even as a boat with a lordly elephant standing in it leans right and left at every step (as it moves on water). As he contemplated on the Soul of the universe as no other than himself, stopping his breath as well as (the function of) his senses, all the worlds as well as their guardian deities resorted for protection to Sri Hari, for they felt much agonized for want of breath. The gods said: O Lord ! we had never known before such (-a sudden) stoppage of breath in the case of all living beings, mobile as well as immobile. Rid us, therefore, of this calamity since we have Sought protection with You, who afford shelter to all. The Lord said : (I find that) Dhruva (son of king Uttanapada) has identified his self with Me (the Soul of the universe); this accounts for the (sudden) stoppage of breath of all of you. Hence be not afraid and return each to your own adode; I shall (presently) deter the child from his penance, which is (otherwise) hard to resist.
Thus ends the eighth discourse, forming part of the Story of Dhruva, in Book Four of the great and glorious Bhagavata-Purana, otherwise known as the Paramahamsa-Samhita.