Vaiśeṣika Sūtra 2.2.16

2.2.16

ādityasaṃyogād bhūtapūrvād bhaviṣyato bhūtāc ca prācī |

āditya-sāṃyogāt—from the conjunction of the sun; bhūta-pūrvāt—past and gone; bhaviṣyataḥ—future; bhūtāt—what has taken place or come into existence; present; ca—and; prācī—east (lit; Orient).

14. (The direction comes to be regarded as) the east, from the past, future, or present conjunction of the sun—93.

[Read sūtra 2.2.14 above]