Puranas and Hindu Holy Scriptures are filled with instructions regarding various aspects of Durga Puja. On the third day of the puja – the third day from Mahalaya – a mirror, vermilion and thin cotton dipped in dye are offered. Usually only a silver coated looking glass is offered as a mirror. But in some instances Darpan – a speculum mirror is also offered.
The darpan mirror is used while bathing the murti of Goddess Durga – whenever there is a ritual bathing of Goddess Durga, it is the reflection on the darpan mirror that is bathed not the original murti.
The darpan is also immersed in a pot of water on the morning of Dasami day when the murtis bid farewell.
It must be noted that many Puranas talk about pujas and rituals that are performed from the Mahalaya day to Dasami day but most of them are not followed today. Today the puja only starts from the sixth day after Mahalaya and the important days are seventh, eighth and ninth.