Khandogya-Upanishad: Second Prapathaka, Tenth Khanda
2. The word Adi (first, Om) has two syllables, the word pratihara has four syllables. Taking one syllable from that over, that is equal (Sama).
3. The word udgitha has three syllables, the word upadrava has four syllables. With three and three syllables it should be equal. One syllable being left over, it becomes trisyllabic. Hence it is equal.
4. The word nidhana has three syllables, therefore it is equal. These make twenty-two syllables.
5. With twenty-one syllables a man reaches the sun (and death), for the sun is the twenty-first from here; with the twenty-second he conquers what is beyond the sun: that is blessedness, that is freedom from grief.
6. He obtains here the victory over the sun (death), and there is a higher victory than the victory over the sun for him, who knowing this meditates on the sevenfold Saman as uniform in itself, which leads beyond death, yea, which leads beyond death.