Devibhagavatapurana 11.16.81

11.16.81

brahmātmane tatsaviturhṛdayāya namastathā |
viṣṇvātmane vareṇyaṃ ca śirase nama ityapi ||

Now I am speaking of the Amganyâsa. Hear. Om tat savitur Brahmâ tmane hridayâya namah (referring to the heart.)
Om Varenyam Visnvâ tmane S’irase namah (referring to the head); Om bhargo devasya Rudrâtmane S’ikhâyai namah (referring to the crown of the head); Om dhîmahi S’aktyâtmane Kavachâya namah (referring to the Kavacha); Om dhîyoyonah Kâlâtmane netratrayâya namah (referring to the three eyes); Om prachodayât sarvâtmane astrâya namah (referring to the Astra or armour, protecting the body). Now I am speaking of the Varnanyâsa. O Great Muni! Hear. This Varnanyâsa is performed by the letters in the Gâyatrî mantra. If anybody does this, he becomes freed of sins.
“Om Tat namah” on the two toes; (touching them).
“Om Sa namah” on the two heels; (touching them).
“Om Vi namah” on the legs;
“Om Tu namah” on the two knees;
“Om Va namah” on the two thighs;
“Om re namah” on the anus;
“Om ni namah” on the generative organ;
“Om ya namah” on the hip;
“Om bha namah” on the navel;
“Om Rgo namah on the heart;
“Om De namah” on the breasts;
“Om va namah” on the heart;
“Om sya namah” on the throat;
“Om dhî namah” on the mouth;
“Om ma namah” on the palate;
“Om hi namah” on the tip of the nose;
“Om dhi namah” on the two eyes;
“Om yo namah” on the space between the eye-brows;
“Om yo namah” on the forehead;
“Om nah namah” to the east;
“Om pra namah” to the south;
“Om cho namah” on the west;
“Om da namah” on the north;
“Om yâ namah” on the head;
“Om ta namah” on the whole body from head to foot.

Some Jâpakas (those who do the Japam) do not approve of the above nyâsa. Thus the Nyâsa is to be done. Then meditate on the Gâyatrî or the World-Mother. The beauty of the body of the Gâyatrî Devî is like that of the full blown Javâ flower. She is seated on the big red lotus on the back of the Hansa (Flamingo); She is holding the red coloured garland on Her neck and anointed with red coloured unguent. She has four faces;
every face has two eyes.
On her four hands are a wreath of flowers, a sacrificial ladle, a bead, and a Kamandalu.
She is blazing with all sorts of ornaments.
From the Devî Gâyatrî has originated first the Rig veda.
Brahmâ worships the virgin Gâyatrî;
on the idea of S’rî Parames’varî Gâyatrî has four feet.
The Rig Veda is one;
the Yajurveda is the second, the Sâmaveda is the third and the Atharva veda is the fourth foot.
The Gâyatrî has eight bellies;
the east side is the one;
the south is the second;
the west is the third;
the north is the fourth;
the zenith is the fifth;
the nadir is the sixth;
the intermediate space is the seventh and all the corners are the eighth belly.
Gâyatrî has seven S’iras (heads);
Vyâkaranam (Grammar) is one;
S’iksâ is the second (that Amga of the Veda, the science which teaches the proper pronunciation of words and laws of euphony);
Kalpa is the third (the Vedânga which lays down the ritual and prescribes rules for ceremonial and sacrificial acts);

Nirukta is the fourth (the Vedânga that contains glossarial explanation of obscure words, especially those occurring in the Vedas);
Jyotish or astronomy is the fifth;
Itahâsa (history) and Purânas is the sixth head;
and Upanisadas is the seventh head.
Agni (fire) is the mouth of Gâyatrî;
Rudra is the S’ikhâ (the chief part);
Her gotra (lineage) is Sâmkhyâyana;
Visnu is the heart of Gâyatrî and Brahmâ is the armour of Gâyatrî.
Think of this Mahes’varî Gâyatrî in the middle of the Solar Orb.
Meditating on the Gâyatrî Devî as above, the devotee should shew the following twenty-four Mudrâs (signs by the fingers, etc., in religious worship) for the satisfaction of the Devî:-- (1) Sanmukh;
(2) Sampût;
(3) Vitata (4) Vistrita;
(5) Dvîmukha;
(6) Trimukha;
(7) Chaturmukha;
(8) Panchamukha;
(9) Sanmukha;
(10) Adhomukha;
(11) Vyâpaka;
(12) Anjali;
(13) S’akata (14) Yamapâs’a;
(15) fingers intertwined end to end;
(16) Vilamba (17) Mustika;
(18) Matsya;
(19) Kûrma;
(20) Varâha;
(21) Simhâkrânta;
(22) Mahâkrânta;
(23) Mudgara;
(24) Pallava.
Next make japam once only of one hundred syllabled Gâyatrî.
Thus twenty-four syllabled Sâvitrî, “Jâtavedase sunavâma, etc.,” forty-four syllabled mantra;
and the thirty two syllabled mantra, “Tryamvakam Jajâmahe, etc.” These three mantras united make up one hundred lettered Gâyatrî.
(The full context of the last Mantra is this:-- Om Haum Om yum sah - Trayamvakam yajâmahe Sugandhim Pusti Vardhanam.

Urbhârukamiva bandhanân mrityo mûksiya ma mritât Bhur Bhhuvah.
Svarom Yum Svah Bhurbhuvah Svarom Haum.) Next make japam of Bhurbhuvah Svah, twenty four lettered Gâyatrî with Om.
O Nârada!
The Brâhmanas are to perform daily the Sandhyo pâsânâ repeating Gâyatrî, completely adopting the rules above prescribed and then he will be able to enjoy completely pleasures, happiness and bliss.
Here ends the Sixteenth Chapter of the Eleventh Book on the description of Sandhyâ Upâsânâ in the Mahâpurânam S’rî Mad Devî Bhâgvatam of 18,000 verses by Maharsi Veda Vyâsa.