Devibhagavatapurana 11.17.7

11.17.7

turīyapādo gāyatryāḥ parorajase sāvadom |
dhyānamasya pravakṣyāmi japasāṅgaphalapradam ||

The Turîya pâda (foot) of Gâyatrî is the mantra “Parorajase Sâvodomâ prâpat.” (Brihad. up. v.14.7). Salutation to Thy beautiful Fourth Foot which is above the Trilokî (Râjas). This cannot obtain that. The presiding deity of this mantra is Brahmâ. I am now speaking of the full Dhyânam (meditation) of this Brahmâ so that the full fruit of the Japam (recitation) may be obtained. There is a full blown lotus in the heart; its form is like the Moon, Sun, and the Spark of Fire; i.e., of the nature of pranava and nothing else. This is the seat of the inconceivable Brahmâ. Think thus. Now on that seat is seated well the steady constant subtle Light, the essence of Akâs’a, the everlasting existence, intelligence and bliss, the Brahmâ. May He increase my happiness (see page 107 the daily practice of the Hindus by R. B. Sris Chandra Basu, on the Invocation of the Gâyatrî).
Note:-- Aum! Gâyatryasyekapadî dvîpadî, tripadî, chatuspadasi, nahi padyase namaste turyâya dars’ atâya padâya parorajase, sâvado mâprâpat O Gâyatrî! Thou art of one foot (in the farm of Trilokî), of two feet (the Trayî vidyâ from Thy second foot) of three feet all Prâna, etc., are Thy third foot and of four feet (as the Purusa). Thou art without foot because Thou art not obtained. Salutation to Thy beautiful fourth foot which is above the Trilokî (Râjas). This cannot obtain that.