The Wealth of Nations by Part 5 Chapter 2 Page 45

Some landlords, instead of a rent in money, require a rent in kind, in corn, cattle, poultry, wine, oil, etc.; others, again, require a rent in service. Such rents are always more hurtful to the tenant than beneficial to the landlord. They either take more or keep more out of the pocket of the former than they put into that of the latter.

In every country where they take place the tenants are poor and beggarly, pretty much according to the degree in which they take place. By valuing, in the same manner, such rents rather high, and consequently taxing them somewhat higher than common money rents, a practice which is hurtful to the whole community might perhaps be sufficiently discouraged.

When the landlord chose to occupy himself a part of his own lands, the rent might be valued