Although silver objects are known from as long ago as the Predynastic period, the metal was very rare for a long time. Before the Middle Kingdom only small objects were made of silver, such as amulets and beads. It becomes more common in the Middle Kingdom, mainly in the form of jewellery such as that found at Dahshour and Lahun. The so-called treasure of El-Tod from the time of Amenemhat II (12th Dynasty), which includes 153 silver bowls, is also famous. Not until the 18th Dynasty did it become more usual to make objects of silver. A number of objects, including mirrors, have been found in the tombs of princesses. The tomb of Tutankhamun contained relatively little silver, but one famous object is a silver trumpet. From the 21st and 22nd Dynasties, a large number of silver objects were found in the tombs of the kings at Tanis, including for example a silver sarcophagus belonging to Sheshonq II and canopic boxes. Textual evidence indicates that for a long time silver was more valuable than gold because it was so rare. By the end of the Middle Kingdom, however, gold had become more valuable than silver. From that time until late in the 19th Dynasty the price ratio stayed more or less the same, as illustrated by ostraca listing trade transactions: gold was worth roughly twice as much as silver, and about two hundred times as much as copper. Silver was used to make beads and jewellery, as well as bowls and vases. It was also beaten to make silver leaf to cover the wooden parts of furniture. For example, a headrest belonging to Hetepheres, the wife of Seneferu and the mother of Khufu, was covered with silver leaf, as were parts of the clothing of Tutankhamun and his wife in the scene on the back of the king's throne.