The great cartographic dais sat upon the western margin of the central round hall, a raised platform of green-stone twelve paces square, polished to the smoothness of a royal mirror.
Qiao Ming knelt in the center of the green stone, his bare feet tucked beneath his thighs. Around him lay the physical record of his life’s labor: forty-eight rolls of cured sheepskin parchment, each roll wrapped in a protective sleeve of boiled sharkskin tied with greased leather thongs. The edges of the skins were yellowed, stiffened by salt spray and rubbed thin along the margins where his thumbs had unrolled them against the boat sides of skiffs and the stone railings of drowned temples. He had cured these skins himself in the upper galleries of the early entry halls, soaking the raw hides in dogfish oil and wood ashes before scraping the wool with a blunt iron draw-knife.
Beside him, Yan Zhiqiu had set down four heavy bronze weights shaped like sleeping turtles to hold the corners of the master chart flat against the stone. The turtles were cast from dark river-bronze, their back shells worn smooth by the handling of forgotten mapmakers.
The master chart was six arm-lengths long and three arm-lengths wide, pieced together from twelve matched skins of northern mountain rams. Across its surface, drawn in fine willow charcoal and fixed with thinned mutton varnish, lay the deep-water survey of the one thousand entry halls. Every sounding point was marked with a tiny cross and a number…
