My research hasn't been able to uncover anything specific about the Day of Purification of all Things. One would assume it would be very much what it suggests. Purification was part of life in Ancient Egypt, the purpose was to empower the senses in different ways, such as the power of insight. Purifying the whole body was an essential part of holy practices. There were divine lakes for purification in their temples. Egyptian priests bathed several times a day, and the priests often shaved all the hair from their bodies to allow them to be purified as much as possible.
Myrrh, Lotus and Sandalwood oils were widely used in Ancient Egyptian purification rituals and the ankh has also been thought by many scholars as being an aquatic symbol representing water in these rituals.
Many of the Gods of Egypt are depicted bearing an Ankh. Sometimes they would extend the ankh to the Pharaoh, indicating both the gift of life and the purification of the subject.