When the toll upon carriages of luxury, upon coaches, post-chaises, etc. is made somewhat higher in proportion to their weight, than upon carriages of necessary use, such as carts, wagons, etc. the indolence and vanity of the rich is made to contribute in a very easy manner to the relief of the poor, by rendering cheaper the transportation of heavy goods to all the different parts of the country.
Adam Smith, John Ramsay McCulloch (1870). “An Inquiry Into the Nature and Causes of the Wealth of Nations”