The following indicate astral travel in yogic thought.
42. By Perfectly Concentrated Meditation and the correlation of the body with the Ether–and by thinking of it as “light as thistle-down”–will come the Power to Traverse the Ether.
43. When that condition of Consciousness is reached–which is far-reaching and not confined to the body; which is outside the body and not conditioned by it–then the Veil which conceals the Light is worn away.
The Yoga Sutras Of Patanjali, Vibhuti Pada(book 3) Verses 42-43
3.41 By self-control over the relation of the body to the ether, and maintaining at the same time the thought of the lightness of cotton, one is able to pass through space.
3.42 By self-control on the mind when it is separated from the body- the state known as the Great Transcorporeal- all coverings are removed from the Light.
3.43 Mastery over the elements arises when their gross and subtle forms,as well as their essential characteristics, and the inherent attributes and experiences they produce, is examined in self-control.
3.44 Thereby one may become as tiny as an atom as well as having many other abilities, such as perfection of the body, and non-resistence to duty.
Although the following translation claims that section of the sutras does not refer to astral projection but rather pertains to levitation:
III. 42. kaya-akasayoh sambandha-samyamat laghu-tula-samapatteh ca akasagamanam
By communion (samyama) on the inter-connections (sambandha) within and between the etheric body (kaya-akashayoh) – while opening up that connection (sambandha) — one becomes absorbed (samapatteh) in the power of the upward (laghu) etheric motion (akasa-gamanam) like a single cotton fiber (tula) moving conjointly with the etheric waves. Thus the power of lightness and weightlessness is experienced — levitation is then easily accomplished.