BṚHADĀRAṆYAKA UPANISHAD · 4.3.20

ता वा अस्यैता हिता नाम नाड्यो यथा केशः सहस्रधा भिन्नस् तावताणिम्ना तिष्ठन्ति ।
शुक्लस्य नीलस्य पिङ्गलस्य हरितस्य लोहितस्य पूर्णाः ।
अथ यत्रैनं घ्नन्तीव जिनन्तीव हस्तीव विच्छाययति गर्तम् इव पतति ।
यद् एव जाग्रद् भयं पश्यति तद् अत्राविद्यया मन्यते ।
अथ यत्र देव इव राजेवाहम् एवेदं सर्वो ऽस्मीति मन्यते ।
सो ऽस्य परमो लोकः ॥

tā vā asyaitā hitā nāma nāḍyo yathā keśaḥ sahasradhā bhinnas tāvatāṇimnā tiṣṭhanti ।
śuklasya nīlasya piṅgalasya haritasya lohitasya pūrṇāḥ ।
atha yatrainaṃ ghnantīva jinantīva hastīva vicchāyayati gartam iva patati ।
yad eva jāgrad bhayaṃ paśyati tad atrāvidyayā manyate ।
atha yatra deva iva rājevāham evedaṃ sarvo ’smīti manyate ।
so ’sya paramo lokaḥ ॥

'There are in his body the veins called Hitâ, which are as small as a hair divided a thousandfold, full of white, blue, yellow, green, and red. Now when, as it were, they kill him, when, as it were they overcome him, when, as it were, an elephant chases him, when, as it were, he falls into a well, he fancies, through ignorance, that danger which he (commonly) sees in waking. But when he fancies that he is, as it were, a god, or that he is, as it were, a king, or "I am this altogether," that is his highest world.

F. Max Müller · The Upanishads, Sacred Books of the East 15 (1884)