Section 35(2) in The Indian Post Office Rules, 1933
(2)Liquids and substances which liquify easily shall be dispatched in a double receptacle. Between the first receptacle (bottle flask not box etc.) and the second (which shall be a box of metal or of strong wood) some space shall be soft to be filled with saw dust, bran, or some other absorbing material in sufficient quantity to absorb all the liquid contents in the event of breakage.
