Hanuman Chalisa

Begin with the fact that it is forty. Chālīsā is from chālīs, forty, and the poem is named after its own length before it is named after its subject. That tells you what kind of thing it is: something built to be counted through, by somebody who expected to reach the end and know they had. Forty caupāī stand between two dohā at the head and one at the close — a body with doorposts.