योगवासिष्ठः yogavāsiṣṭhaḥ - book-7, chapter-167, verse-20

सर्वदैव च वा तुर्यं तदन्तः सर्वदैव वा ।
तदिदं वा न यद्विद्मो वयमाशान्तरूपिणः ॥ २० ॥

sarvadaiva ca vā turyaṃ tadantaḥ sarvadaiva vā ,
tadidaṃ vā na yadvidmo vayamāśāntarūpiṇaḥ 20

20. Or it is ever in its fourth state of turya, which is beyond all these triple states; but whether it is in this or that or what state, we know nothing of, being ourselves always in a state of disquiet and continued agitation.