Agnipurana 335.6

335.6

prātaḥsavanayogastu chando gāyatramāśritam /
kaṇṭhe mādhyandinayutaṃ madhyamantreṣu bhānugam //

In the morning pressing (prātaḥsavana), it is associated with the Gāyatrī meter; / in the throat, it is connected with the midday pressing, following the sun in the intermediate mantras;