The major first part of the paper collects as exhaustively as possible all mentions of words for ‘mirror’ occuring in Vedic literature (c.1200–300 bce). The occurrences are presented with sufficient context in Sanskrit and English in order to show how and why the mirror was used in Vedic rituals and Vedic culture in general, and what meaning was ascribed to it. The second part of the paper discusses a fact of major significance that emerges from this documentation: in the extensive older Vedic literature of the Saṃhitās, Brāhmaṇas, Āraṇyakas and Śrautasūtras (excepting the late Kātyāyana-Śrautasūtra), there is no reference to the mirror at all. This suggests that the mirror was not known in Vedic India until it was introduced to South Asia by the Persian Empire at the end of the sixth century bce. The later Vedic literature, starting with the early Upaniṣads and comprising also the Gṛhyasūtras and Kātyāyana-Śrautasūtra, would therefore postdate 500 bce. In other words, the ‘mirror’ words seem to offer a criterion that for the first time enables a division of the Vedic literature into two clearly separate phases of development. Equally important is the firm historical basis that the mirror provides for dating the transition point.