The Marquis de Sade wrote to his wife in a letter dated May 16, 1779, complaining about the quality of a care package he had received while in prison. Among the requests that he made for future deliveries were for cookies that "must smell of chocolate, as if one were biting into a chocolate bar." This phrasing is highly suggestive of chocolate bars being eaten by themselves and not just grated into chocolate-based drinks, as was a far more common use at this time. Such a product would predate the invention of the cocoa press by Coenraad Johannes van Houten and other innovations which made chocolate suitable for mass-production. In 1847, Joseph Fry discovered a way to mix the ingredients of cocoa powder, sugar and cocoa to manufacture a paste that could then be molded into a solid chocolate bar for consumption. Inspired by Fry, John Cadbury, founder of Cadbury, introduced his brand of the chocolate bar in 1849. That same year, Fry and Cadbury chocolate bars were displayed publicly at a trade fair in Bingley Hall, Birmingham. Fry's chocolate factory, J. S. Fry & Sons of Bristol, England, began mass-producing chocolate bars and they became very popular. Over 220 Fry's products were introduced in the following decades, including Fry's Chocolate Cream bar in 1866, the first chocolate Easter egg in the UK in 1873, and Fry's Turkish Delight (or Fry's Turkish bar) in 1914. In addition to Cadbury and Fry, Rowntree's and Terry's were major British chocolate companies, as chocolate manufacturing expanded in England throughout the rest of the century. Milk chocolate was invented in Switzerland by Daniel Peter and Henri Nestlé in 1875. Rodolphe Lindt, a Swiss confectioner and inventor, began adding cocoa butter as an ingredient in 1879. The addition of cocoa butter allowed the chocolate bar to keep its shape and melt in the mouth. In 1897, following the lead of Swiss companies, Cadbury introduced its own line of milk chocolate bars in the UK. Cadbury Dairy Milk, first produced in 1905, became the company's best selling bar. In the United States, immigrants who arrived with candy-making skills drove the development of new chocolate bars. Milton S. Hershey, a Pennsylvania caramel maker, saw a German-manufactured chocolate-making machine at the 1893 Chicago World's Fair. He immediately ordered one for his Lancaster factory and produced the first American-made milk chocolate bar. In Canada, Ganong Bros., Ltd. of St. Stephen, New Brunswick developed and began selling their version of the modern chocolate bar in 1910.