Chānd-Mül, 1879-84FOURTH KHANDA
1. Let a man meditate on the syllable Om, for the udgitha is sung beginning with Om. And this is the full account of the syllable Om:-
Chānd-Śaṃ, 8th c. A.D.om ity etad ityādiprakṛtasyākṣarasya punar upādānam udgīthākṣarādyupāsanāntaritatvād anyatra prasaṅgo mā bhūd ity evam artham | prakṛtasyaivākṣarasyāmṛtābhayaguṇaviśiṣṭasyopāsanaṃ vidhātavyam ity ārambhaḥ | om ity ādi vyākhyātam || 1 ||
http://www2.hf.uio.no/common/apps/permlink/permlink.php?app=polyglotta&context=record&uid=cb9eb6d7-8e41-11ee-937a-005056a97067