Four principal dialects of classical Sanskrit
According to Tiwari (1955), there were four principal dialects of classical Sanskrit:
paścimottarī (Northwestern, also called Northern or Western),
madhyadeśī (lit., middle country),
pūrvi (Eastern) and
dakṣiṇī (Southern, arose in the Classical period).
The predecessors of the first three dialects are even attested in Vedic Brāhmaṇas, of which the first one was regarded as the purest (Kauṣītaki Brāhmaṇa, 7.6).