Taittirīyopaniṣat 01.18

पृथिव्यन्तरिक्षं द्यौर्दिशोऽवान्तरदिशाः। अग्निर्वायुरादित्यश्चन्द्रमा नक्षत्राणि। आप ओषधयो वनस्पतय आकाश आत्मा। इत्यधिभूतम्। अथाध्यात्मम्। प्राणोव्यानोऽपान उदानः समानः। चक्षुः श्रोत्रं मनो वाक् त्वक्। चर्म मांसं स्नावाऽस्थिमज्जा। एतदधि विधाय ऋषिरवोचत्। पाङ्क्तं वा इदग्म् सर्वम्। पाङ्क्तेनैव पाङ्क्तं स्पृणोतीति ॥१८॥

pṛthivyantarikṣaṃ dyaurdiśo'vāntaradiśāḥ। agnirvāyurādityaścandramā nakṣatrāṇi। āpa oṣadhayo vanaspataya ākāśa ātmā। ityadhibhūtam। athādhyātmam। prāṇovyāno'pāna udānaḥ samānaḥ। cakṣuḥ śrotraṃ mano vāk tvak। carma māṃsaṃ snāvā'sthimajjā। etadadhi vidhāya ṛṣiravocat। pāṅktaṃ vā idagm sarvam। pāṅktenaiva pāṅktaṃ spṛṇotīti ॥18॥

[पृथिवि (pṛthivi) - earth; अन्तरिक्षम् (antarikṣam) - atmosphere; द्यौः (dyauḥ) - sky; दिशः (diśaḥ) - directions; अवान्तरदिशाः (avāntaradiśāḥ) - intermediate directions; अग्निः (agniḥ) - fire; वायुः (vāyuḥ) - wind; आदित्यः (ādityaḥ) - sun; चन्द्रमाः (candramāḥ) - moon; नक्षत्राणि (nakṣatrāṇi) - stars; आपः (āpaḥ) - waters; ओषधयः (oṣadhayaḥ) - herbs; वनस्पतयः (vanaspatayaḥ) - trees; आकाशः (ākāśaḥ) - space; आत्मा (ātmā) - ego-principle; इति (iti) - thus; अधिभूतम् (adhibhūtam) - pertaining to elements; अथ (atha) - now; अध्यात्मम् (adhyātmam) - pertaining to self; प्राणः (prāṇaḥ) - prāṇa (vital breath); व्यानः (vyānaḥ) - vyāna (diffusive breath); अपानः (apānaḥ) - apāna (downward breath); उदानः (udānaḥ) - udāna (upward breath); समानः (samānaḥ) - samāna (equalizing breath); चक्षुः (cakṣuḥ) - eye; श्रोत्रम् (śrotram) - ear; मनः (manaḥ) - mind; वाक् (vāk) - speech; त्वक् (tvak) - skin; चर्म (carma) - hide; मांसम् (māṃsam) - flesh; स्नावाः (snāvāḥ) - sinews; अस्थि (asthi) - bone; मज्जा (majjā) - marrow; एतत् (etat) - this; अधि (adhi) - over; विधाय (vidhāya) - having arranged; ऋषिः (ṛṣiḥ) - sage; अवोचत् (avocat) - said; पाङ्क्तम् (pāṅktam) - fivefold; वा (vā) - indeed; इदम् (idam) - this; सर्वम् (sarvam) - all; पाङ्क्तेन (pāṅktena) - by fivefold; एव (eva) - only; पाङ्क्तम् (pāṅktam) - fivefold; स्पृणोति (spṛṇoti) - fills; इति (iti) - thus;]

Earth, atmosphere, sky, directions, and intermediate directions; fire, wind, sun, moon, and stars; waters, herbs, trees, space, and ego-principle — these are the elements. Now, pertaining to spiritual knowledge (adhyātmam): prāṇa, vyāna, apāna, udāna, and samāna; eye, ear, mind, speech, and skin; hide, flesh, sinews, bone, and marrow. Having arranged these, the sage declared: "All this is indeed fivefold. By the fivefold alone, the fivefold is completed."

Taittirīya Bhāshya 01.18

The word 'ātmā' in this context refers to the principle of ego. A reference is provided to a testimonial from Tattvasaṁhitā where Lord Hari, beginning with Nārāyaṇa empowers the six groups of five elements.

"पृथिव्याद्यं पाङ्क्तषट्कं पाङ्क्तेनैव स्वयं हरिः। नारायणादिरूपेण बलयत्यञ्जसा प्रभुः। इत्युवाच स्वयं विष्णुः वेदद्रष्टा गुणाधिकः॥"

"pṛthivyādyaṃ pāṅktaṣaṭkaṃ pāṅktenaiva svayaṃ hariḥ। nārāyaṇādirūpeṇa balayatyañjasā prabhuḥ। ityuvāca svayaṃ viṣṇuḥ vedadraṣṭā guṇādhikaḥ॥"

[पृथिव्या (pṛthivyā) - by the earth; आद्यं (ādyaṃ) - the first; पाङ्क्तषट्कं (pāṅktaṣaṭkaṃ) - six groups of five; पाङ्क्तेनैव (pāṅktenaiva) - by the very fivefold; स्वयं (svayaṃ) - himself; हरिः (hariḥ) - Hari (Viṣṇu); नारायणादिरूपेण (nārāyaṇādirūpeṇa) - in the form beginning with Nārāyaṇa; बलयति (balayati) - empowers; अञ्जसा (añjasā) - directly; प्रभुः (prabhuḥ) - the Lord; इति (iti) - thus; उवाच (uvāca) - said; स्वयं (svayam) - himself; विष्णुः (viṣṇuḥ) - Viṣṇu; वेदद्रष्टा (vedadraṣṭā) - the seer of the Veda; गुणाधिकः (guṇādhikaḥ) - one who is superior in qualities;]

"Lord Hari himself, in the form beginning with Lord Nārāyaṇa, empowers the six groups of five elements beginning with earth by the fivefold principle; thus spoke Lord Viṣṇu himself, the seer of the Veda and one endowed with supreme qualities."

इति तत्त्वसंहितायाम्॥

iti tattvasaṁhitāyām॥

[इति (iti) - thus; तत्त्वसंहितायाम् (tattvasaṁhitāyām) - in the Tattvasaṁhitā;]

- stated thus in the Tattvasaṁhitā.

आत्मा अहङ्कारतत्त्वम्॥

ātmā ahaṅkāratattvam॥

[आत्मा (ātmā) - self; essence; soul; अहङ्कार (ahaṅkāra) - ego; I-maker; तत्त्वम् (tattvam) - principle; reality;]

The word 'ātmā' in this context refers to the principle of ego.