An entire lake floated in Chen Changsheng's body.
Yes, this was an entire lake, not just one side of a lake. This lake floated in the air, not so stingy as to give the observer only one side to appreciate1.
When Chen Changsheng had performed Meditative Introspection for the first time, he had seen this lake, but the vast majority of his mind had been focused on the snowy plain. The moment he had seen the lake, he was stunned and could not understand it. Right afterwards, he had fallen unconscious due to the blazing of his snowy plain, so he had no chance to carefully observe this lake.
