Hiranyakeshigrihyasutra 2.5.14

We shall explain (the festival of) the Ashtakâ.

The eighth day of the dark fortnight that follows after the full moon of Mâgha, is called Ekâsntakâ.

On the day before that Ashtakâ, under (the Nakshatra) Anûrâdhâs, in the afternoon he puts wood on the fire, strews southward-pointed and eastward-pointed Darbha grass around it, and turns rice out of four shallow cups over which he has laid one purifier, with (the Mantra), 'I turn out, impelled by the god Savitri, this cake prepared from four cups (of rice), which may drive away all suffering from the Fathers in the other world. On the impulse of the god Savitri, with the arms of the two Asvins, with Pûshan's hands I turn thee out, agreeable to the fathers, the grandfathers, the great-grandfathers.'

With the same purifier he silently strains the Prokshanî water; he silently sprinkles (with that water the rice and the vessels), silently husks (the rice), silently bakes it in four dishes like a Purodâsa, sprinkles (Âgya) on it, takes it from the fire, sprinkles (water) round (the fire) from right to left, and puts a piece of Udumbara wood on (the fire). With the (spoon called) Darvi which is made of Udumbara wood, he cuts off in one continual line which is directed towards south-east, (the Avadâna portions) one after the other, spreading under and sprinkling over them (Âgya), and sacrifices them, one after the other, in one continual line which is directed towards south-east, with (the Mantras), 'The mortars, the pressing-stones have made their noise, preparing the annual offering. Ekâshtakâ! May we be rich in offspring, in valiant sons, the lords of wealth. Svadhâ! Adoration!
'God Agni! The cake which is prepared with ghee and accompanied by (the word) svadhâ, that the Fathers may satiate themselves—(this our) offering carry duly, Agni. I, the son, sacrifice an oblation to my fathers. Svadhâ! Adoration!
'Here is a cake, Agni, prepared from four cups (of rice), with ghee, rich in milk, in wealth, in prosperity. May the Fathers gladly accept it all together; may it be well sacrificed and well offered by me. Svadhâ! Adoration!'

Then he makes oblations of (other) food with (the verses), 'The one who shone forth as the first,' 'The Ekâshtakâ, devoting herself to austerities,' 'She who shone forth as the first' (Taitt. Samhitâ IV, 3, 11, I. 3. 5).

Cutting off (the Avadânas destined for the Svishtakrit oblation) together from the cake and from the (other) food and mixing them with clarified butter, he makes an oblation thereof with (the formula), 'To Agni Kavyavâhana Svishtakrit svadhâ! Adoration!'

That (cake) with ghee and honey and with the food (mentioned in Sûtras 5. 6) he touches in the way prescribed for the Srâddha ceremony and puts down lumps (of it) according to the ritual of the Pinda offerings.

(The remains of) that (cake, &c.) he serves to learned Brâhmanas.

He gives them food and presents as at the Srâddha ceremony.

The known (rites) down to the pouring out of the handfuls of water (are performed here) as at the monthly (Srâddha).