“Where is my cyanometer,” Thoreau exclaimed in his journal on a blue-skied spring day, referring to the curious device invented by the Swiss scientist Horace-Bénédict de Saussure a century earlier to measure the blueness of the sky. 

Here are some of the most beautiful meditations on blue from 200 years of literature, including Thoreau, Goethe, Toni Morrison, Rachel Carson, Virginia Woolf, Rebecca Solnit, Georgia O'Keeffe, and other titans of the world in words.