Apastambagrihyasutra 8.21: ekaviṃśaḥ khaṇḍaḥ

The times for the monthly Srâddha are in the second fortnight (of the month), as they are stated.

Let him feed, without regard of (worldly) purposes, pure Brâhmanas, versed in the Mantras, who are not connected with himself by consanguinity or by their Gotra or by the Mantras (such as his teacher or his pupils), an odd number, at least three.

He makes oblations of the food (prepared for the Brâhmanas) with the next (verses, II, 19,1-7);

Then the Âgya oblations (indicated by the) next (Mantras, II, 19, 8-13).

Or invertedly (i.e. he offers Âgya with the verses referred to in Sûtra 3, and food with those referred to in Sûtra 4).

Let him touch the whole (food) with the next (formulas, II, 19, 14-16).

Or the (single) prepared (portions of food destined) for the single Brâhmanas.

Having caused them with the next (formula, II, 20, 1) to touch (the food, he gives it to them to eat).

When they have eaten (and gone away), he goes after them, circumambulates them, turning his right side towards them, spreads out southward-pointed Darbha grass in two different layers, pours water on it with the next (formulas, II, 20, 2-7), distributes the Pindas, ending in the south, with the next (formulas, II, 20, 8-13), pours out water as before with the next (formulas, 14-19), worships (the ancestors) with the next (formulas, II, 20, 20-23), sprinkles with the next (verse, 24) water three times from right to left round (the Pindas) with a water-pot, besprinkles the vessels, which are turned upside down, repeating the next Yagus (25) at least three times without taking breath, sets up the vessels two by two, cuts off (Avadânas) from all (portions of food), and eats of the remains at least one morsel with the next Yagus (26).

In the evening before that day (he performs) the preparatory ceremony.

He bakes a cake of four cups (of rice).

(The cake is prepared) in eight dishes (like a Purodâsa), according to some (teachers).