《天工开物·上篇·乃服》
当茧衣结成之后，每盆炭火再添上半斤炭，使温度升高。蚕吐出的丝随即干燥，所以这种丝能经久不坏。
茧绪既成，即每盆加火半斤，吐出丝来随即干燥，所以经久不坏也。
As the cocoon forms, a half catty of charcoal will be added to each brazier, so as to increase the temperature. The silk from the silkworms will be dried up soon, so the silk can last longer.