The Wealth of Nations by Part 5 Chapter 2 Page 157

other direct taxes upon the wages of labour.

Article IV: Taxes which, it is intended, should fall indifferently upon every different Species of Revenue

The taxes which, it is intended, should fall indifferently upon every different species of revenue, are capitation taxes, and taxes upon consumable commodities.

These must be paid indifferently from whatever revenue the contributors may possess; from the rent of their land, from the profits of their stock, or from the wages of their labour.

Capitation Taxes

Capitation taxes, if it is attempted to proportion them to the fortune or revenue of each contributor, become altogether arbitrary. The state of a man’s fortune varies from