Srimad Bhagvata Mahapurana: Book 3: Chapter 11: Verses 28-41
Again, when the night (of universal dissolution) sets in, the moon and the sun as well disappear and all the three worlds, viz., Bhuh, Bhuvah and Swat) get reabsorbed into his body. (How this happens is described now.) When the three worlds are being consumed by the divine energy in the shape of fire emitted by the mouth of Lord Sankarsana (the serpent-god), the sages Bhrgu and others (who have their abode in the Maharloka, immediately above Indra's paradise) feel oppressed by the heat (of that huge conflagration) and ascend from the Maharloka to the Janaloka (the next higher world). Meanwhile all the seven oceans exceed their limits at the approach of universal destruction. Their waters get unusually swollen and with their waves tossed by boisterous and fearful gusts of wind they submerge all the three worlds in no time. In the midst of that (vast expanse of) water lies Sri Hari on His couch of Lord Ananta (Sesa), His eyes closed on account of sleep in the form of abstract meditation, the inhabitants of the Janaloka extolling Him (on all sides). With the alternation of days and nights of the above description, which can be (easily) deduced from the (constant) flux of time, the hundred years even of Brahma's life which is the longest in this creation, are well-nigh spent. One-half of Brahma's life is called Parardha. The first Parardha has already expired and the second is now running (has commenced from the current Kalpa). The first Parardha opened with a momentous Kalpa, the Brahma Kalpa, in which appeared Brahma, whom the wise recognize as Veda personified. The Kalpa that marked the end of the same Parardha is called the Padma Kalpa, in which sprang from the pool of Sri Hari's navel the lotus representing all the worlds. The present has been declared as the opening Kalpa of the second Parardha, O Vidura, (a scion of Bharata). It is known by the name of Varaha-Kalpa, inasmuch as Sri Hari took the form of a boar in this Kalpa. The aforesaid period of two Parardhas is figuratively spoken of as the mere twinkling of an eye of the immutable, immortal, beginningless Lord, the Soul (origin) of the universe. This all-powerful Time, ranging from a Paramanu (the smallest measure) to the length of two Parardhas, has no control over the all-embracing Lord; it holds sway only on those who have identified themselves with the body and all that is associated with it.This egg-shaped universe, constituted as it is of the eight causal principles (vii., Primordial Matter, the Mahat-tattva, the Ego and the five subtle elements) and the sixteen evolutes (viz., the mind, the five senses of perception, the five organs of action and the five gross elements, none of which evolves further), has a breadth of five million Yojanas (or forty million miles) and is covered outside by seven sheaths (viz., earth; water, fire, air, ether, the Ego and the Mahat-tattva), each of which is ten times larger than the one it surrounds. That cause of all causes, in which this universe with all its covering sheaths looks like a Paramanu, and which comprises myriads of other universes, is called the indestructible Brahma; and that is the transcendent reality of the most ancient Person, Lord Visnu, the Supreme Spirit in embodied form.
Thus ends the eleventh discourse in Book Three of the great and glorious Bhagavata-Purana, otherwise known as the Paramahamsa-Samhita.