Narapatijayacarya 5.5.7

in the asterism Pūrvā[ṣāḍhā], bhu-dha-pha-ḍha in the pillar belonging to the southwestern quarter. / Ārdrā [and so forth], the fourfold pillar, is to be understood by the knowers of sounds.

On "the hundred-square diagrammatic wheel" (cakraṃ śatapadam): I shall explain the hundred-square diagrammatic wheel, the diagrammatic wheel with one hundred cells. Of what kind is it? "Arising from the quarters of the asterisms and phonemes" (bhapādākṣasaṃbhavam): bha means lunar mansion; each of them has four divisions; it is produced from them, composed of them. Just as the quarters of the lunar mansions and zodiacal signs are to be known there from the initial phonemes of the names. On "transverse and vertical" (tiryagūrdhvagatā): the wise man should draw lines numbering Rudra, [namely] eleven in number, going horizontally and going vertically. When this is done, one hundred squares are produced. On "he should place [the phonemes] beginning with a, va, ha, ḍa" (nyasedavahaḍādīni): in order, successively, in the directions beginning with the northeast, one should arrange in order the five pure phonemes each, beginning with a-va-ka-ha-ḍa. The meaning of this is: beginning from the northeastern cell, in the five cells of the eastern row, he should write the pentad of phonemes, namely a-va-ka-ha-ḍa. In this manner, from the southeastern corner cell, in the southern row, [he should write] the five phonemes ma-ṭa-pa-ra-ta. From the southwestern corner cell, in the western row, he should write the five phonemes na-ya-bha-ja-ṣa. From the northwestern corner cell, in the northern row, he should write the five phonemes ga-śa-da-ca-la. On "from combination with the five vowels" (pañcasvarasamāyogāt): from combination with the five vowels, that is, from association and conjunction with them in the form of a, i, u, e, o, make each single consonant into five forms; as va, vi, vu, ve, vo; ka, ki, ku, ke, ko; ha, hi, hu, he, ho; ḍa, ḍi, ḍu, ḍe, ḍo;