Kauṣītaki Upaniṣad 3.4

3.4

Speech gives up to him (who is absorbed in prâna) all names, so that by speech he obtains all names. The nose gives up to him all odours, so that by scent he obtains all odours. The eye gives up to him all forms, so that by the eye he obtains all forms. The ear gives up to him all sounds, so that by the ear he obtains all sounds. The mind gives up to him all thoughts, so that by the mind he obtains all thoughts. This is the complete absorption in prâna. And what is prâna is pragñâ (self-consciousness), what is pragñâ (self-consciousness) is prâna. For together do these two live in the body, and together do they depart.
Now we shall explain how all things become one in that pragñâ (self-consciousness).