The Purāṇas divide time into such components as yugas, as four age cycles, and kalpa s, which are a day and a night of Brahmā. The Purāṇas provide a very thorough analysis of these components. Together with doctrines concerning the various destructions (pralayas), they are the glue that holds this cosmology together and provides it with a coherent drama of salvation. Indeed Viṣṇu Purāṇa asserts it is not space but time that constitutes the body of the deity. Hindu divisions of time are as follows. Fifteen "twinklings of the eye" make a kāṣṭhās, or one kalā; and thirty kalās equal one muhūrtta. Thirty muhūrttas constitute a day and a night of mortals; thirty such days make a month, which is divided into two halves (waxing and waning). Six months form an ayana, and two ayanas compose a year. The southern ayana is a night and the northern a day of the gods. Twelve thousand divine years, each comprising 360 such days, constitute the period of the yugas (caturyuga). The kṛtayuga consists of four thousand divine years, the tretāyuga of three thousand, the dvāparayuga of two thousand, and the kaliyuga of one thousand. The period that precedes a yuga is called a sandhyā; it lasts for as many hundred years as there are thousands in the yuga. The sandhyānsa, at the end of the yuga, is of similar duration. Together the four yugas constitute a kalpa. A thousand kalpas is a day of Brahmā, and fourteen Manus, or descendants of man, reign during that time period, which is known as Manvantara. At the end of a day of Brahmā, the universe is consumed by fire, and its dissolution occurs. Brahmā then sleeps for a night of equal duration. Three hundred and sixty such days and nights constitute a year of Brahmā, and one hundred such years equal his entire life (mahākalpa). One parārddha, or half his life, has expired. The various pralayas epitomize the agency of time by moving the soul—and the universe—from its current state to its eventual salvation. The Purāṇas distinguish four types of dissolution, or pralaya, each reversing the process of creation at different levels. These include: 1. Nitya pralaya, or physical death of the individual caught in the cycle of transmigration; 2. Ātyantika pralaya, or spiritual liberation (mokṣa) ; 3. Prākṛta pralaya, or dissolution of the elements at the end of the life of Brahmā; 4. Naimittika pralaya, or occasional dissolution associated with the cycles of yugas and descents of avatāras. Yet calculations of time also had a meditative quality: the contemplation of infinity, or the largest number next to infinity, was meant to be close to a vision of God. The Brahmavaivarta Purāṇa tells the well-known story of the dialogue between Viṣṇu and Indra. In the form of a young boy, Viṣṇu tells Indra that a parade of ants crawling on the earth have all had lives as Indras—each ruling over their own solar systems in different ages.