The source presents Koshi Bharana as an observance connected to a special vow, or Mannat. It describes a sugarcane canopy, fruit, prasad and lamps between evening and morning Arghya.
Fulfilling Special Vows: The Koshi Ritual
Koshi Bharana is a special, highly revered ritual within Chhath Puja performed by families who have taken a specific vow (Mannat): often for the birth of a child, the curing of a severe illness, or a major life success.
How It Is Performed
On the evening of Sandhya Arghya, families construct a canopy using 5 to 7 sugarcane stalks in their courtyard or at the riverbank. Underneath this canopy, earthen lamps (diyas), fruits, and traditional Prasad are arranged. The diyas are kept continuously lit throughout the night until the morning Usha Arghya, symbolizing the burning light of unwavering faith.