The Wealth of Nations by Part 5 Chapter 2 Page 160

first poll-tax were assessed at three shillings in the pound of their supposed income, were afterwards assessed as gentlemen. In the assessment of a tax which was not very heavy, a considerable degree of inequality had been found less insupportable than any degree of uncertainty.

In the capitation which has been levied in France without any interruption since the beginning of the present century, the highest orders of people are rated according to their rank by an invariable tariff; the lower orders of people, according to what is supposed to be their fortune, by an assessment which varies from year to year.

The officers of the king’s court, the judges and other officers in the superior courts of justice, the officers of the troops, etc., are assessed in the first manner.