Eyck – was the only piece of Netherlandish art on display there. More large panels were added to the collection after the French conquered the Low Countries. These works had a profound effect on German literary critic and philosopher Karl Schlegel, who after a visit in 1803 wrote an analysis of Netherlandish art, sending it to Ludwig Tieck, who had the piece published in 1805. In 1821 Johanna Schopenhauer became interested in the work of Jan van Eyck and his followers, having seen early Netherlandish and Flemish paintings in the collection of the brothers Sulpiz and Melchior Boisserée in Heidelberg. Schopenhauer did primary archival research because there was very little historical record of the masters, apart from official legal documents. She published Johann van Eyck und seine Nachfolger in 1822, the same year Gustav Friedrich Waagen published the first modern scholarly work on early Netherlandish painting, Ueber Hubert van Eyck und Johann van Eyck; Waagen's work drew on Schlegel and Schopenhauer's earlier analyses. Waagen went on to become director of the Gemäldegalerie in Berlin, amassing a collection of Netherlandish art, including most of the Ghent panels, a number of van der Weyden triptychs, and a Bouts altarpiece. Subjecting the works to meticulous analysis and examination in the course of acquisition, based on distinguishing characteristics of individual artists, he established an early scholarly system of classification. In 1830 the Belgian Revolution split Belgium from the Netherlands of today; as the newly created state sought to establish a cultural identity, Memling's reputation came to equal that of van Eyck in the 19th century. Memling was seen as the older master's match technically, and as possessing a deeper emotional resonance. When in 1848 the collection of Prince Ludwig of Oettingen-Wallerstein at Schloss Wallerstein was forced onto the market, his cousin Prince Albert arranged a viewing at Kensington Palace; though a catalogue of works attributed to the School of Cologne, Jan van Eyck and van der Weyden was compiled by Waagen, there were no other buyers so Albert purchased them himself. At a period when London's National Gallery sought to increase its prestige, Charles Eastlake purchased Rogier van der Weyden's The Magdalen Reading panel in 1860 from Edmond Beaucousin's "small but choice" collection of early Netherlandish paintings. Netherlandish art became popular with museum-goers in the late 19th century. At the beginning of the 20th century, van Eyck and Memling were the most highly regarded,