From the Ku Yü Thu

(Illustrated Record of Ancient Jade Objects) by Chu Tê-Jun of +1341:

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The picture on the right  is the ornamental (figure) on a (model) south-pointing carriage. By standard measure it was 1.42 ft. high and 7.4 inches long. The (vertical) shaft rose through a hole 3.7 inches in diameter, its own diameter being 3.4 inches. At the top it carried a human figure carved in jade, with one hand constantly indicating the south. 
The shaft penetrated down through the hole and turned around on its axis. The figure (was represented as) treading upon (an image of) Chhih-Yu. In the Yen-Yu reign-period (+1314 to + 1320) I myself saw this (model) at the house of the Senior Academician Yao Mu-An. The colour of the jade was pale reddish-yellow.....
Source: Needham. Joseph: Science and Civilization in China, Volume 4, Part II, 1965