Bhagavata Purana 11.28.20
Srimad Bhagavatam · 28 · Verse 20
Sanskrit Original
विज्ञानमेतत्त्रियवस्थमङ्ग गुणत्रयं कारणकार्यकर्तृ । समन्वयेन व्यतिरेकतश्च येनैव तुर्येण तदेव सत्यम् ॥ २० ॥
vijñānam etat triy-avastham aṅga guṇa-trayaṁ kāraṇa-kārya-kartṛ samanvayena vyatirekataś ca yenaiva turyeṇa tad eva satyam
The material mind manifests in three phases of consciousness — wakefulness, sleep and deep sleep — which are products of the three modes of nature. The mind further appears in three different roles — the perceiver, the perceived and the regulator of perception. Thus the mind is manifested variously throughout these threefold designations. But it is the fourth factor, existing separately from all this, that alone constitutes the Absolute Truth.