The Ṛgveda, the first and the foremost of the four Vedas, consists of 10,552 mantras or verses. There are two well-known systems of dividing these mantras into books, sections or chapters. As per the first system which groups the mantras according to the deities, topics and metres, the Ṛgveda is divided into ten ‘maṇḍalas’, each maṇḍala being subdivided again into ‘anuvāka’ and ‘sūkta’. Though this method is good from the standpoint of study, it is not good from the standpoint of memorization (which had a supreme place in ancient Vedic studies) since there is a large variation in the number of mantras in each maṇḍala. Hence an attempt was made later to divide the whole of the Ṛgveda into eight sections, each called an ‘aṣṭaka,’ keeping the total number of mantras in each aṣṭaka almost the same. Each aṣṭaka was again sub-divided into eight ‘adhyāyas’ or chapters and the adhyāyas into ‘vargas’ or groups. The vargas consisted of the mantras. Due care has been taken to maintain the total number of akṣaras or letters in each aṣṭaka the same, since some mantras are in longer metres.
The following table gives an idea of this division:
Performance of religious rites in honour of the dead ancestors exists in all the societies of the world, in some form or the other. The ‘aṣṭakā’ (also known as ‘aṣṭaka-śrāddha’) is a Vedic rite enjoined to be performed in honour of the pitṛs or ancestors (aṣṭaka = pitṛ, ancestor). The name is also derived from the fact that it has to be done on the eighth day (aṣṭakā = of the eighth day) of the dark fortnights of the four months—Mārgaśīrṣa, Pauṣa, Māgha and Phālguna (November to February). Though it is meant for the pitṛs or ancestors, deities like Viśvedevas, Agni and Sūrya are also mentioned as the recipients of the offerings. The total number of such rites is generally three. Cooked vegetables, cakes and even flesh are the offerings.
Sometimes the rites are compressed into one rite spread over three days or even one day in the month of Māgha (Jan.-Feb.).