Devasana Purnima, also known as Snan Yatra is a festival dedicated to Lord Jagannath. It is observed on the Purnima or full moon day. It is observed on the Jyestha month in the Hindu calendar and is said to be one of the oldest festivals. It is celebrated just before the Rath Yatra of Lord Jagannath in Puri, Deva Snan is a ritualistic bathing ceremony of the deities of the Jagannath Temple- Lord Jagannath, Devi Subhadra, and Lord Balabhadra. As per Skanda Purana, when Raja Indradyumna installed the wooden deities, he arranged this bathing ceremony, and hence, the day is celebrated to bathe the trinity. While Puri attracts thousands of visitors this day. It is celebrated grandly in Bengal as well. The idols of Lord Jagannath, Devi Subhadra, and Lord Balabhdra are taken out from the temple, early in the morning and brough to the bathing altar.
The water which is used for bathing the three deities are taken from the three deities are taken from the well inside the temple. There are certain rituals are also followed after the Devasnana where a total of 108 pitchers of herbal and aromatic water are used to bath the trinity. As the deities are then dressed up in Sada Besha after the bath, the idols of Lord Jagannath, Devi Subhadra and Lord Baladhra in the Hathi Besha. At night the deities are put to rest in the Anasara period, the devotees are prohibited from viewing the idols. Which only appears for the public viewing only after 15 days, on the day just before the famous Rath Yatra.