There are no holes in the bottom of the pot, that's precisely what's so special about this type of ceramic steam cooker: The juices are saved inside! A pure broth containing only the flavors and nutrients extracted by the steam, all of which are lost in a traditional steamer.
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In the town of Jianshui, during the reign of Emperor Qianlong of the Qing Dynasty, a potter by the name of Yang Li created a ceramic steam-pot with a hollow tube in the middle. This special design made possible the preparation a unique medicinal soup...
More on the history of the Steamer.