《太平广记·卷四百六十四·水族一》
北方的荒野中有个石湖，方圆有千里，湖岸有五丈多深，长年结冰，只有夏至前后五六十天才解冻。
北方荒中有石湖，方千里，岸深五丈余，恒冰，唯夏至左右五六十日解耳。
There was a stone lake in the northern wilderness with a radius of thousands of miles. The banks of the lake were more than five meters deep. The lake was frozen all year round, and it only thawed for 50 or 60 days before and after the summer solstice.