The sources of History can be divided in three categories. First is 'remembered' history, that is, what has come down to us from the past in the shape of manuscripts and literary works, and what in recent years has assumed great importance, 'oral history'. Thus this category of sources ''ranges from the personal recollections claimed by the elders to the living traditions of a civilization, as embodied in its scriptures, its classics, and its inherited historiography. It may be described as the collective memory of a community or nation or other entity - what it, or its rulers and leaders, poets, and sages, choose to remember as significant, both as reality and symbol.''
Religion manifested itself in almost all the activities of the early men, and therefore, it is not surprising that the earliest literature available to us is in the form of earliest literature available to us is in the form of religious texts.
Buddhist literature are important sources for the history of Buddhism and its royal patrons like Ashoka. They also uncover aspects of political, social and economic conditions of the times.
The Tipitaka (3 Pitakas – The Three Baskets/Collections) lay down the tenets and principles of Buddhism. The Tipitaka, written in Pali, consists of three books: (a) the Sutta Pitaka, containing the sermons of the Buddha (b) the Vinaya Pitaka, which has rules for Buddhist monks and nuns, and (c) the Abhidhamma Pitaka, which contains a systematic arrangement of the teachings of the Sutta Pitaka.
The Jatakas, composed in the 3rd century BC - 2nd century AD, relate stories of the previous births of the Buddha. They have also served to give a glimpse of the social history of the period.
Buddhaghosha, in the 5th century AD, wrote a commentary on the Tipitaka. The Sri Lankan Chronicles from the 5th century – the Dipavamsa and the Mahavamsa – deal with the Buddha's life, the Buddhist councils, emperor Ashoka and the kings of Sri Lank.