Some words of Adam Smith below. He was as most would guess a harsh critic of taxes on labor. He also wrote that taxes on profits were a disincentive. These things seem like common sense to most now.
1. "The subject of every State ought to contribute towards the support of the government, as nearly as possible, in proportion to their respective abilities; that is, in proportion to the revenue which they respectively enjoy under the protection of the State."
2. "The tax each individual is bound to pay ought to be certain, and not arbitrary. The time of payment, the manner of payment, and the quantity to be paid, ought all to be clear and plain to the contributor, and to ever other person."
3. "Every tax ought to be levied at the time, or in the manner in which it is most likely to be convenient for the contributor to pay it."
4. "Every tax ought to be so contrived as both to take out and to keep out of the pockets of the people as little as possible, over and above what it brings into the public treasury of the State."
Edit to add: "In all cases, a direct tax upon the wages of labour must, in the long run, occasion both a greater reduction in the rent of land, and a greater rise in the price of manufactured goods, than would have followed from a proper assessment of a sum equal to the produce of the tax, [levied] partly upon the rent of land, and partly upon consumable comodities."
