Jaiminīya Upaniṣad Brāhmaṇa 2.6.5

2.6.5

sa yadi brūyāt pañca ma āgāyeti prāṇa udgītha ity eva vidvān pañca manasā dhyāyet
pañca hi prāṇo 'pāno vyānas samāno 'vānaḥ
pañca haivāsyājāyante /

If he should say: “Chant for me for five”, knowing that breath is the udgītha, he should mentally focus on five.
For breath, out-breath, diffused breath, equalized breath, and downward breath are five.
Five indeed are born to him.