The Mukhya Upaniṣads

Māṇḍūkya · Om and the Four Quarters of the Self

Mantra 4

स्वप्नस्थानोऽन्तःप्रज्ञः सप्ताङ्ग एकोनविंशतिमुखः प्रविविक्तभुक्तैजसो द्वितीयः पादः ॥ ४ ॥

In plain words

The second quarter is Taijasa: its field is dream, its awareness is inward, it has seven limbs and nineteen mouths, and it experiences subtle objects.