In his book, Inventing Kindergarten, Norman Brosterman (1997) displays the work of 20th-century artists and architects such as Wassily Kandinsky, Paul Klee, Piet Mondrian, Le Corbusier, and Frank Lloyd Wright alongside photographs of colourful instructional materials used by those who followed the educational philosophies of the German pedagogue Friedrich Froebel. Froebel's method, widely adopted in schools throughout Europe and to some extent in America in the 19th century, made use of carefully prepared manipulative materials he called class="EmphasisTypeItalic ">gifts. These materials included blocks, balls, wooden forms for design work, paper for weaving and cutting, jointed slats, sewing or "beauty" forms, and coloured parquetry shapes. Brosterman speculates that these artists may have drawn upon their early experiences as children in Froebelian-inspired kindergartens, incorporating these simple but infinitely variable gifts as essential elements of their aesthetic vocabularies.