Section 2(2) in The Indian Post Office Rules, 1933
(2)On postal articles other than letters, letter cards, and post cards posted for transmission by air at any post office in India, an air mail fee of rupee 2/- for the first fifty grams or fraction thereof and Rs. 1/- for every additional fifty grams or fraction thereof, shall be chargeable in addition to the postage and other charges payable under the rules.
