Hast thou entered into the treasures of the snow? The "treasures of the snow" are the storehouses, wherein the snow is, poetically, supposed to be laid up. Vast accumulations of snow actually exist in various portions of the earth's surface, but the fresh snow that falls is not taken from these treasuries, but newly generated by the crystallization of floating vapours in the atmosphere.
Or hast thou seen the treasures of the hail? This expression is to be explained similarly, as poetical. Hail is nowhere kept in store. It is generated by the passage of rain-drops through a layer of freezing air.