Chandogya Upanishad 4.5.1

4.5.1

atha ha enam ṛṣabho 'bhyuvāda satyakāma3 iti \
bhagava iti ha pratiśuśrāva \
prāptāḥ somya sahasraṃ smaḥ \
prāpaya na ācāryakulam \\405.1\

then the bull spoke to him, saying: ‘Satyakāma!’ ‘Sir!’ he replied. ‘We have reached a thousand, my dear. Bring us to the teacher’s house. And let me tell you a quarter of Brahma.’ ‘Tell me, Sir.’ To him it then said: ‘One sixteenth is the east. One sixteenth is the west. One sixteenth is the south. One sixteenth is the north. This, verily, my dear, is the quarter of Brahma, consisting of four sixteenths, named the Shining.