Vaisesika Sūtra 2.2.14

आदित्य संयोगाद् भूतपूर्वाद् भविष्यतो भूताच्च प्राची ॥१४॥

āditya saṁyogād bhūtapūrvād bhaviṣyato bhūtācca prācī ॥14॥

[आदित्य (āditya): From the Sun; संयोग (saṃyoga): Conjunction or combination; आद् (ād): From; भूतपूर्वाद् (bhūtapūrvād): From the past existences; भविष्यतो (bhaviṣyato): From the future; भूताच्च (bhūtācca): And from the present; प्राची (prācī): East; प्राच् (prāc): East;]

The direction east emerges by the combination of the Sun with the past, the future, and the present.