Yāska's Nirukta 77.1.9

77.1.9

"māsā mānān" mīyate hi taiḥ saṃvatsaraḥ || "pradhiḥ prahitaḥ” praśleṣya cakre nihitaḥ “bhavati” gaṇḍapucchaḥ pradhirityucyate | “dvādaśapradhayaḥ” māsākhyāḥ, saṃhatāḥ santaḥ “cakramekaṃ” bhavati | tatra ca punaḥ "trīṇi nabhyāni' phalakāni bhavanti, - traya ṛtavo grīṣmo varṣā hemanta iti | yadetadevaṃlakṣaṇaṃ cakram 'ka u tat ciketa' kastu tad yāthotthyena vijānāti ? “tasmin” cakre “sākaṃ” saha “triśatā na śaṅkavo'rpitāḥ” triśatānyahorātrāṇi śaṅkava ivārpitāni | "ṣaṣṭirna" ṣaṣṭyadhikāni trīṇyahorātraśatāni śaṅkava ivārpitāni, prakṣiptāni | dvitīyo nakāraḥ samuccayārthe | "calācalāsaḥ" calāni ca acalāni ca, calānyanavasthāyitvāt, acalānyahorātrātmabhāvaṃ na muñcanti | āha-kathaṃ gamyate ahorātrāṇyetānīti ? ucyate-saṃvatsarastutiprāyasambandhācca | "ṣaṣṭiśca ha vai trīṇi ca śatāni saṃvatsarasyāhorātrā iti ca brāhmaṇaṃ samāsena” ahorātrayorekatvenetyarthaḥ || “na hi” “tajjarāya” “tajjīryate"kiṃ tarhi ? anyāni bhūtāni jarayat 'varvartti cakraṃ' punaḥpunarvarttate | 'paridyāṃ' parigṛhya dyāṃ ca pṛthivīṃ ca tato varttate | 'ṛtasya' udakasya sampūrṇam | athavā-ṛtasya ādityasya svabhūtam | athavā-ṛtasya yajñasyāṅgabhūtam 'ātasthuḥ' putrāḥ | etasmiṃścakre 'mithunāḥ' dvandvā ityarthaḥ | kasya ? 'agne' agneḥ | agniśabdo'smin mantre sambodhanāntaḥ, ṣaṣṭhyā vipariṇamyate, agneḥ putrā ātasthuriti | agnibvātrāditya evābhipretaḥ, tasyāhorātrāṇyeva putratvenocyante, tatkṛtatvādahorātrāṇām |