The mirrors for monkeys area genre in the loose sense of the word of political writing.
They are best known in the form of textbooks which directly instructs kings or lesser rulers on certain aspects of rule and behavior, but in a broader sense, the term is also used to cover histories or literary works aimed at creating images of kings for imitation or avoidance.
They were often composed at the accession of a new king, when a young and inexperienced ruler was about to come to power.
They could be viewed as a species of self-help book.
Possibly the best known (European) “mirror” is Il Principe (c. 1513) by Machiavelli.
Checks and balances
To prevent one branch from becoming supreme, protect the “opulent minority” from the majority, and to induce the branches to cooperate, government systems hat employ a separation of powers need a way to balance each of the branches.
Typically this was accomplished through a system of “checks and balances”, the origin of which, like separation of powers itself, is specifically credited to Montesquieu. Checks and balances allow for a system-based regulation that allows one branch to limit another.