Abu Rayhan Biruni Islamic polymath
al-Biruni (973–1048) was among the first to investigate khutu, which he referred to as
al-chutww. He described it as being from the land of the
Kirgiz in the northern part of the Turkish territory and mentioned that it was in great demand in Egypt. He noted that the material came in a variety of colours, with yellowish-green being best, followed by those coloured
camphor,
white, "like the sun", and dark grey. He also mentioned the beliefs that the material came from the forehead of the
roc (an enormous bird from Arabic and Persian myths which was said to carry off and eat elephants) or the forehead of a hippopotamus, but did not seem to attach much weight to these ideas, noting that it was much more similar to the frontal bone of a bull or goat. He wrote: "It originates from an animal; it is much in demand, and preserved in the treasuries among the Chinese who assert that it is a desirable article because the approach of poison causes it to exude."
Ibn al-Husayn Kashgari Writing shortly after al-Biruni,
Kashgari mentioned khutu in his work
Diwan Lughat at-Turk (c. 1075): "Horn of a sea fish imported from China. It is (also) said that it is the root of a tree. It is used for knife handles. The presence of poison in food is put to the test by it because when broth or other dishes in the bowl are stirred with it the food cooks without fire (if poison is present in it), or if the horn is placed on a bowl it (the horn) sweats without steam."
Ibn al-Akfani The next investigation of khutu was by
Ibn al-Akfani (1286–ca. 1348-49), who called the material
chartut. Although he cited al-Biruni's earlier work, he disagreed with a number of Al-Biruni's conclusions. For example, he favoured the theory that khutu came from the forehead of a large bird. He also offered a slightly different spectrum of possible colours for khutu (yellow, red,
apricot, dust, black), though he did agree that the quality of the material varied with the colour. ==Modern scholarship==