Varaha Puranam describes Sraddha Kalpa by Sage Markandeya to Sage Gurmukh.
The number of Brahmins invited for Sradhha Kalpa should be in Odd numbers - like one, three, five. While performing the Sradhha of Maternal Grand Father, it is compulsory to perform Vaishyadeva Sradhha simultaneously . While performing Sradhha Kalpa related to the deities, the Brahmins should have their food facing East. In case of Sradhha Kalpa related to the ancestors, the Brahmins should have their food facing North.
During the entire course of Sradhha rite, the Yagjyopaveetham should be worn in the opposite position. The offerings of sesame seeds, water and Kusha grass (Dharba) are made for the sradhha rites of ancestors. The performer of Sradhha should be seated on the Kusha Grass. It is customary to scatter the sesame seeds on the place where the Brahmins were fed. It is believed that the food partake are for the ancesstors to satiate them. Chanting of 'Rakshodhana Mantra' is also compulsory.
Offering of 'Pinda' with sesame seeds and water on the Kusha grass is one of the important parts of the ritual, placing them on South. The Pinda is offered in the name of the deceased and their ancestors.
Jai Sriman Narayana !!