From his 1776 Thoughts on Government:
The principle difficulty lies, and the greatest care should be employed in constituting this representative assembly. It should be in miniature an exact portrait of the people at large. It should think, feel, reason and act like them. That it may be the interest of this assembly to do strict justice at all times, it should be an equal representation, or, in other words, equal interests among the people should have equal interests in it. Great care should be taken to effect this, and to prevent unfair, partial, and corrupt elections. Such regulations, however, may be better made in times of greater tranquility than the present; and they will spring up themselves naturally, when all the powers of government come to be in the hands of the people’s friends. At present, it will be safest to proceed in all established modes, to which the people have been familiarized by habit.
Of course, we also know that “the masses” are irrational, later on in the essay Mr. Adams tells us about the separation of powers.