...half an ounce in weight, to or from the United States, shall be five cents for any distance in Canada. Every additional weight of half an ounce, or additional...weight of less than half an ounce, to be charged as an additional rate. 5. Upon all letters posted in the United States to be delivered in Canada, or posted...

...and every letter or parcel not exceeding half an ounce in weight shall be deemed a single letter; and every additional weight of half an ounce, or additional weight of less than half an ounce, shall be charged with an additional single rate of postage. And there shall be charged for letters...