Chinese literature is full of examples of men and women who applied themselves to their books with untiring diligence. Some tied their hair to the beam of their humble cottage so that when they nodded with sleepiness the jerk would awake them and they might return to their books.
Others slept upon globular pillows that when they became so restless as to move and cause the pillow to roll from under their head they might get up and study.
The child once more took the blocks and illustrated how 
one who was so poor as to be unable to furnish himself with candles, confined a fire-fly in a gauze lantern using that instead of a lamp. At the same time he explained that another who was perhaps not able to afford the gauze lantern, studied by the light of a glowworm.
"K'ang Heng," said the child, as he put the blocks together in a new form, "had a still better way, as well as more economical. His house was built of clay, and as the window of his neighbor's house was immediately opposite, he chiseled a hole through his wall and thus took advantage of his neighbor's light.
"Sun K'ang's method was very good for winter," continued the child as he rearranged the blocks, "but I do not know
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