This line feels deeply Romantic because it uses nature to point to something larger than what the reader can comprehend. Frost takes a simple image, a ladder leaning into an apple tree, and turns it into a symbol of exhaustion, and a desire to reach beyond. Romantic writers believe nature has a kind of spiritual power, and the ladder pointing “toward heaven” reflects how the author feels his work ascending into a higher feeling. It’s not necessarily about religion, rather than feeling a higher power or something divine through the natural world. In this moment, the physical scene opens a door into emotion and imagination, which signifies Romanticism, because it portrays life being shaped by a divine power.