It is one of the sacred periods in the Vedic calendar. During this sacred month of Purattasi (Ashwina) which generally falls in September/October, Lord Balaji is said to have made his appearance on earth in human form as Sri Venkateshwara (Lord of Tirupati). 

All Saturdays are considered very auspicious. During this month of Purattasi, Lord Venkateshwara is prayed to and worshipped on Saturdays which is a favorite day for the Lord. A maavillaku is lit with ghee to worship Lord Venkateshwara. It is the belief that the Lord will be able to bless all the devotees who are far away from Tirupati hills through the rays of the maavillakku light. 

Puja Diya

To make the maavilakku, mix 1 cup rice flour with ¾ cup powdered jaggery, ¼ cup grated coconut and a pinch of cardamom powder. Add a couple of spoons of melted ghee to help shape the flour mixture like a diya or lamp with a hollow to fill in with a couple more spoons of ghee. Place a cotton wick in the ghee and light the flour lamp.