The speaker pictures an old illuminated manuscript, where the main text is rigid, solemn and dull: God, philosophy, lists of dead kings and what they owned. The margins, though, are open space, and the speaker fills them with whatever she likes. Animals, tiny harvesters, meadow flowers, and a group singing Gilbert and Sullivan crowd in, which is a funny, anachronistic touch.
The most striking image sits in a corner: a woman giving birth alone under a tree, her hair white, and the baby's hair white too. The speaker calls it "my little joke," but it feels quietly serious, as if ordinary, female, bodily life is being slipped in where official history leaves it out. The tone is playful and a little defiant. While the main text "drones on," the speaker claims the margins as "mine" and decorates them with lapis, carnelian and gold, treating her own small world as the real treasure.