Aitareya Āraṇyaka 2.3.5

2.3.5

tad vā idaṃ bṛhatīsahasraṃ saṃpannam \
tad dhaitad eke nānāchandasāṃ sahasraṃ pratijānate, kim anyat, sad anyad brūyāmeti \
triṣṭupsahasram eke.
jagatīsa/hasram eke.
'nuṣṭupsahasram eke \
tad uktam ṛṣiṇā \
anuṣṭubham anu carcūryamā/ṇam (RV X 124,9c), indraṃ ni cikyuḥ kavayo manīṣā- (RV X 124,9d) -iti \\
vāci vai tad aindraṃ prāṇaṃ nyacāyann ity etat tad uktaṃ bhavati \
sa heśvaro yaśasvī kalyāṇakīrti/r bhavator.
īśvaro ha tu purāyuṣaḥ praitor iti ha smāha-.
-akṛtsno hy eṣa ātmā, yad vāg.
abhi hi prāṇena manase 'syamāno vācā nānu/bhavati \
bṛhatīm abhisaṃpādayed.
eṣa vai kṛtsna ātmā, yad bṛhatī \
so 'yam ātmā sarvataḥ śarīraiḥ parivṛtas.
tad yathāyam ātmā sarvataḥ śarīraiḥ parivṛta, evam eva bṛhatī sarvataś chandobhiḥ parivṛtā \
madhyaṃ hy eṣā/m aṅgānām ātmā, madhyaṃ chandasāṃ bṛhatī \
sa heśvaro yaśasvī kalyā/ṇakīrtir bhavator.
īśvaro ha tu purāyuṣaḥ praitor iti ha smāha.
kṛtsno hy eṣa ātmā, yad bṛhatī.
tasmād bṛhatīm evābhisaṃpādayet \\ 5 \\

This (nishkevalya-sastra) becomes perfect as a thousand of Brihatî verses.

Some teachers (belonging to a different Sâkhâ) recognise a thousand of different metres (not of Brihatîs only). They say: 'Is another thousand (a thousand of other verses) good? Let us say it is good.'

Some say, a thousand of Trishtubh verses, others a thousand of Gagatî verses, others a thousand of Anushtubh verses.

This has been said by a Rishi (Rv. X, 124, 9):--

'Poets through their understanding discovered Indra dancing an Anushtubh.' This is meant to say: They discovered (and meditated) in speech (called Anushtubh)--at that time (when they worshipped the uktha)--the Prâna (breath) connected with Indra.

He (who takes the recited verses as Anushtubhs) is able to become celebrated and of good report.

No! he says; rather is such a man liable to die before his time. For that self (consisting of Anushtubhs) is incomplete. For if a man confines himself to speech, not to breath, then driven by his mind, he does not succeed with speech.

Let him work towards the Brihatî, for the Brihatî (breath) is the complete self.

That self (gîvâtman) is surrounded on all sides by members. And as that self is on all sides surrounded by members, the Brihatî also is on all sides surrounded by metres.

For the self (in the heart) is the middle of these members, and the Brihatî is the middle of the metres.

'He is able to become celebrated and of good report, but (the other) able to die before his time,' thus he said. For the Brihatî is the complete self, therefore let him work towards the Brihatî (let him reckon the sastra recitation as a thousand Brihatîs).