'Offering sky lanterns have also been an important ritual in Theravada Buddhist tradition. However, sky lantern is called differently in different regions. Thus it is called khom loi in Thailand and phanush in Bangladesh. The Tai Buddhists of Assam, the followers of Theravada tradition, call it phom phai. Phom phai is a small hot air balloon made of paper with an opening at the bottom where a small fire is suspended. Releasing phom phai or sky lantern in the air is an important event of Pavara— a ritual observed to mark the end of Vasavassa or three-month rain retreat in Theravada tradition. On the day of Pavara, which generally falls in October, the devotees gather together in the mosteries or vihars in the evening and release sky lanterns with joy and merriment. Some do believe that offering sky lanterns to the Buddha will ward off bad luck and bring in good fortune. Buddhist canonical texts, however, say that lighting lanterns help cultivate the wholesome roots of non-greed, non-hatred, and non-delusion. It leads the mind to tranquility by freeing it from the three evil roots, viz., greed, hatred, and delusion. The exact date of sky lantern ritual is unknown. However, a story of the Buddha's life is associated with this practice. As the legend goes, during his stay at Sravasti, the Buddha left for Tavatimsa (heavenly adobe of thirty-three devas) to preach the Abhidhamma to his mother Mayadevi. It was vasvassa (three-month rain retreat) then. He spent whole three months there preaching the Abhidhamma to his mother and other monks gathered there. At the end of rain retreat, he returned to Sankassa, which is now known as a Buddhist holy place, located in Farrukhabad district of Uttar Pradesh. During his journey back to earth, all the gods welcomed him with flowers and garlands and lit lamps to lighten his path. Since then, sky lantern ritual is believed to have started.