Laudator Temporis Acti

Maynard Solomon, "The Quest for Faith," Beethoven Essays (Cambridge: Harvard University Press, 1988; rpt. 1996), pp. 216-229 (at 219, notes omitted):

There seems little doubt that Beethoven's worship of nature had deeply religious overtones. This worship went far beyond the conventional pastoral and arcadian evocations characteristic of the followers of Rousseau and Schiller to border upon religious fervor: "Every tree in the countryside said to me: 'Holy! Holy!' In the forest, enchantment! Who can express it all?" Even more explicit is the passage on a leaf of sketches: "Almighty in the forest! I am happy, blissful in the forest: every tree speaks through you, O God! What splendor! In such a woodland scene, on the heights there is calm, calm in which to serve Him."

Seneca, Letters to Lucilius 41.3 (tr. Richard M. Gummere):

If ever you have come upon a grove that is full of ancient trees which have grown to an unusual height, shutting out a view of the sky by a veil of pleached and intertwining branches, then the loftiness of the forest, the seclusion of the spot, and your marvel at the thick unbroken shade in the midst of the open spaces, will prove to you the presence of deity.

si tibi occurrerit vetustis arboribus et solitam altitudinem egressis frequens lucus et conspectum caeli densitate ramorum aliorum alios protegentium summovens, illa proceritas silvae et secretum loci et admiratio umbrae in aperto tam densae atque continuae fidem tibi numinis faciet.

John Milton, Elegy 5.131-134 (tr. Walter MacKellar):

The gods themselves are not slow to prefer the forests of earth to heaven,
and every grove has its own deity.
Long let each grove have its deity!
Leave not, O gods, your homes amid the trees.

Dii quoque non dubitant caelo praeponere silvas,
   Et sua quisque sibi numina lucus habet.
Et sua quisque diu sibi numina lucus habeto,
   Nec vos arborea, dii, precor, ite domo.

Caspar David Friedrich (1774-1840), Waldinneres bei Mondschein
(Berlin, Alte Nationalgalerie, accession number NG 12/92)