योगवासिष्ठः yogavāsiṣṭhaḥ - book-7, chapter-83, verse-27

स्वयमन्तः कचत्कान्तिश्चिदाकाशः स्वभावखे ।
अयं सोहमयं च त्वं करोतीत्यादिकल्पनम् ॥ २७ ॥

svayamantaḥ kacatkāntiścidākāśaḥ svabhāvakhe ,
ayaṃ sohamayaṃ ca tvaṃ karotītyādikalpanam 27

27. The intellect expands itself, in itself in its natural state of vacuum; and devolves itself likewise into its conceptions of I and thou and all others.