The poem "The Chambered Nautilus" by Oliver Wendell Holmes tells of a discovery that the poet makes on the seashore. He comes across the broken shell of a chambered nautilus. The chambered nautilus is a type of mollusk. It is related to squids and octopuses, but unlike these other types of mollusks, it carries a lovely coiled shell that protects it from predators. The shell is divided into chambers. The mollusk lives in the outermost chamber, and the others are filled with gas that allows it to maintain buoyancy when it hovers in the water.

Holmes begins the poem by imagining the nautilus as a ship of pearl that has become wrecked upon the shore. He imagines the process the mollusk went through in building its shell chamber by chamber as it grows.

The poet is grateful to the nautilus because of the inspiration that it gives him. He writes of a "heavenly message" that the nautilus imparts that is clearer than a note blown from Triton's horn. It wakens in the poet "deep caves of thought" leading to a "voice that sings."

The poet is inspired to consider his soul as a nautilus. Just as the nautilus builds new chambers as it grows, his soul should leave the past behind and create "more stately mansions" of thought. As his soul grows, the space that the poet creates for it will become "more vast," or larger. Finally, when the poet reaches the end of his life, he will leave the shell of his body behind, just as the nautilus has left its empty shell by the shore of the sea, and the poet's soul will at last be free.