The practice of market segmentation emerged well before marketers thought about it at a theoretical level. Archaeological evidence suggests that Bronze Age traders segmented trade routes according to geographical circuits. Other evidence suggests that the practice of modern market segmentation was developed incrementally from the 16th century onwards. Retailers, operating outside the major metropolitan cities, could not afford to serve one type of clientele exclusively, yet retailers needed to find ways to separate the wealthier clientele from the "riff raff". One simple technique was to have a window opening out onto the street from which customers could be served. This allowed the sale of goods to the common people, without encouraging them to come inside. Another solution, that came into vogue from the late sixteenth century, was to invite favored customers into a back-room of the store, where goods were permanently on display. Yet another technique that emerged around the same time was to hold a showcase of goods in the shopkeeper's private home for the benefit of wealthier clients. Samuel Pepys, for example, writing in 1660, describes being invited to the home of a retailer to view a wooden jack. The eighteenth-century English entrepreneurs, Josiah Wedgewood and Matthew Boulton, both staged expansive showcases of their wares in their private residences or in rented halls to which only the upper classes were invited while Wedgewood used a team of itinerant salesmen to sell wares to the masses.