To see the Summer Sky — Poetry Class

Staring at the ceiling was what Dickinson did in her Poetry class. She believed that true poems flee from the classroom and textbook.

To see the Summer Sky
Is Poetry, though never in a Book it lie－
True Poems flee－

(F.1491/J.1472)

[1] Summer:: a horizontal bearing beam in a building _{(OED n.2 2b)}. sky:: the space near the ceiling _{(OED 6)}.
[2] Poetry:: the name given to the sixth, or class from the bottom or third from the top, in English Roman Catholic schools, seminaries, or colleges, on the continent, and subsequently in England. The class so called comes between Syntax and Rhetoric _{(OED 6)}. Book:: textbook used in the class.
[3] flee:: from the book and classroom.

THIRD CLASS, OR BELLES-LETTRES. English Literature.--Lectures on English Composition, Prose and Poetry ─ Documents of the Assembly of the State of New York (1864)