By the end of the 13th century a few large crosses had been erected in passes and on hills. Examples from this period include the Confin Cross in St. Valentin on the Mals Heath, which also acted as a boundary marker, or crosses on the Arlberg, the Gardena Pass or Birnlücke. An early example of a large cross, visible from the valley floor, being set up on a mountain top, occurred during the first successful climb of Mont Aiguille in 1492, when three crosses were put up at the corner of the summit plateau. In the 16th century crosses were erected with increasing frequency on mountain peaks, especially for the purpose of marking alpine pasture and municipal boundaries. In the 17th century, especially during the Thirty Years' War, these religious symbols gained importance. The crosses of this period were mostly simple wooden ones hewn from branches found near the site, or house crucifixes. During this time crosses were often made with two cross beams in the form of so-called patriarchal crosses (or Scheyern crosses). These weather crosses were intended to supersede the old pagan superstitions associated with thunder, storm and hail. Further layers of Christian imagery as perceived by the Romantic generation made summit crosses a motif favoured by the painter Caspar David Friedrich in more than one of his mystic landscapes.