Someone called Shi Xian was registered in Taiyuan, making his living in trade, and he often travelled with goods to Daibei. In the summer of the second year Changqing (822 CE), he was travelling through the Yanmenguan. Just then the summer heat was especially intense, so he lay down beneath a large tree. He suddenly dreamed of a monk, with wasp-fierce eyes and wearing a patched jacket and robe, very strange in his body-shape, who came before Xian and addressed him: “Our hut is to the south of Wutaishan, and there is the Qionglin Pond, far from the world of mortals, and truly a place for a group of monks to avoid the summer heat. Will our lucky benefactor accompany me there? If unable to, I can see that my benefactor is afflicted by the heat and close to death; [2] would that not be a cause for regret?” Xian was extremely bothered by the temperature, and, as the monk also talked with him of future events, he addressed the monk: “I am willing to go with the master.” The monk then led Xian to the west, and, going several li, there was indeed the Qionglin Pond, and he saw a group of monks in the water. Xian marvelled at this and questioned them, at which the monk said: “This is the moonlight pool. Therefore my disciples bathe in it, and also wash away the great heat.” At this he led Xian around the pond. Xian merely marvelled at the group of monks in the water, and also noticed that none of their forms were particularly different. Before long dusk fell and one of the monks said: “The gracious benefactor should listen to us disciples as we chant scripture.” At this Xian stood by the poolside, and the crowd of monks united their voices in the water and made a great clamour. After a moment, a monk pulled him by the hand, saying: “The gracious benefactor should bathe with us in the moonlight pond; be careful but have no fear.” Xian thus followed the monks into the water, but suddenly felt a great chill over his whole body, shivering and shuddering. At this he awoke with a great shock, to find himself lying back beneath the great tree, with his clothes quite soaking wet, shivering in extreme cold. Night had already fallen when he reached the village hostel. When the next day dawned, his illness had abated slightly, so he took to the road, and along the way he heard the croaking of frogs, sounding just like the monks’ scripture chant. He therefore set out to find them, and after going a few li, came across the Qionglin Pond, where there were very many frogs. That pond was indeed the moonlight pond, and the group of monks were just a bunch of frogs. Xian said: “These frogs can change their shape by magic to delude people; this is nothing short of demonic!” He then killed them all.
Zhang Du 張讀, Xuanshi Zhi 宣室志 (Stories from the Chamber of Dissemination), 1.1-2 (Tale 2):
玄陰池蛙
有石憲者，其籍編太原，以商為業，常行貨於代北。長慶二年夏中於雁門關行道中，時暑方甚，因偃於大木下。忽夢一僧，蜂目，被褐衲，其狀甚異，來憲前，謂曰：「我廬於五臺山之南，有窮林積水，出塵俗甚遠，實羣僧清暑之地。檀越幸偕我而遊乎？卽不能，吾見檀越病熱且死，得 [2] 無悔於心耶？」憲以時暑方盛，僧且以禍福語相動，因謂僧曰：「願與師偕往。」於是其僧引憲西去，且數里，果有窮林積水，見羣僧在水中。憲怪而問之，僧曰：「此玄陰池。故我徒浴於中，且以蕩炎燠。」於是引憲環池行。憲獨怪羣僧在水中，又其狀貌無一異者。已而天暮，有一僧曰：「檀越可聽吾徒之梵音也。」於是憲立池旁，羣僧卽於水中合聲而譟。僅食頃，有一僧挈手曰：「檀越與吾偕浴於玄陰池，慎無懼。」憲卽隋僧入池中，忽覺一身盡冷，噤而戰。由是驚悟。見己卧於大木下，衣盡濕，而寒慄且甚。時已日暮，卽抵村舍中。至明日，病稍愈。因行於道，聞道中忽有蛙鳴，甚類羣僧之梵音。於是徑往尋之，行數里，見窮林積水，有蛙甚多。其水果名玄陰池者，其僧乃羣蛙爾。憲曰：「此蛙能幻形以惑於人，豈非怪之尤者乎！」於是盡殺之。
又見《廣記》卷四七六，題為《石憲》；《紺珠集》卷五，題為《玄陰池》；《類說》卷二三，題為《玄陰池》；《說郛》卷六。《紺珠集》、《類說》、《說郛》引均為節文。
Zhang Du 張讀, Xuanshi Zhi 宣室志 (Stories from the Chamber of Dissemination) in Du yi zhi, Xuanshi Zhi 獨異志，宣室志 (Outstanding Fantastic Stories, Stories from the Chamber of Dissemination), edited by Zhang Yongqin 张永钦 and Hou Zhiming 侯志明 (Beijing: Zhonghua shuju, 1983)
The version transmitted in the Taiping Guangji varies slightly from this:
Shi Xian 石憲
Someone called Shi Xian was registered in Taiyuan, making his living in trade, and often trading in Daibei. In the summer of the second year Changqing (822 CE), he was travelling through the Yanmenguan. Just then the summer heat was especially intense, so he lay down beneath a large tree. He suddenly dreamed of a monk, with wasp-fierce eyes and wearing a patched jacket and robe, very strange in his body-shape, who came before Xian and addressed Xian, saying: “Our hut is to the south of Wutaishan, and there is the Qionglin Pond, far from the world of mortals, and truly a place for a group of monks to avoid the summer heat. Will our lucky benefactor accompany me there? If unable to, I can see that my benefactor is afflicted by the heat and close to death; [2] would that not be a cause for regret?” Xian was extremely bothered by the temperature, and, as the monk also talked with him of future events, he addressed the monk: “I am willing to go with the master.” The monk then led Xian going west, and, going several li, there was indeed the Qionglin Pond, and he saw a group of monks in the water. Xian marvelled at this and questioned them, at which the monk said: “This is the moonlight pool. Therefore my disciples bathe in it, and also wash away the great heat.” At this he led Xian around the pond. Xian merely marvelled at the group of monks in the water, and also noticed that none of their forms were particularly different. Before long dusk fell and one of the monks said: “The gracious benefactor should listen to us disciples as we chant scripture.” At this Xian stood above the pond, and the crowd of monks united their voices in the water and made a great clamour. After a moment, a monk pulled him by the hand, saying: “The gracious benefactor should bathe with us in the moonlight pond; be careful but have no fear.” Xian thus followed the monks into the water, but suddenly felt a great chill over his whole body, shivering and shuddering. At this he awoke with a great shock, to find himself lying back beneath the great tree, with his clothes quite soaking wet, shivering in extreme cold. Night had already fallen when he reached the village hostel. When the next day dawned, his illness had abated slightly, so he took to the road, and along the way he heard the croaking of frogs, sounding just like the monks’ scripture chant. He therefore set out to find them, and after going a few li, came across the Qionglin Pond, where there were very many frogs. That pond was indeed the moonlight pond, and the group of monks were just a bunch of frogs. Xian said: “These frogs can change their shape by magic to move people; this is nothing short of demonic!” He then killed them all. From Xuanshizhi.
Li Fang 李昉, et al., Taiping guangji 太平廣記 (Extensive Gleanings from the Period of Great Harmony), 10 vols (Beijing: Zhonghua shuju, 1961), x, 476.3917:
石憲
有石憲者。其籍編太原。以商為業。常貨於代北。長慶二年夏中。雁門關行道中。時暑方盛。因偃於大木下。忽夢一僧。蜂目被褐衲。其狀甚異。來憲前。謂憲曰。我廬於五臺山之南。有窮林積水。出塵俗甚遠。實羣僧清暑之地。檀越幸偕我而遊乎。卽不能。吾見檀越病熱且死。得無悔於心耶。憲以時暑方盛。僧且以禍福語相動。因謂僧曰。願與師偕去。於是其僧引憲西去。且數里。果有窮林積水。見羣僧在水中。憲怪而問之。僧曰。此玄陰池。故我徒浴於中。且以蕩炎燠。於是引憲環池行。憲獨怪羣僧在水中。又其狀貌無一異者。已而天暮。有一僧曰。檀越可聽吾徒之梵音也。於是憲立池上。羣僧卽於水中合聲而譟。僅食頃。有一僧挈手曰。檀越與吾偕浴於玄陰池。慎無懼。憲卽隋僧入池中。忽覺一身盡冷噤而戰。由是驚悟。見己卧於大木下。衣盡濕。而寒慄且甚。時已日暮。卽抵村舍中。至明日。病稍愈。因行於道。聞道中忽有蛙鳴。甚類羣僧之梵音。於是徑往尋之。行數里。窮林積水。有蛙甚多。其水果名玄陰池者。其僧乃羣蛙。而憲曰。此蛙能易形以感於人。豈非怪尤者乎。於是盡殺之。出宣室志
Zhiguai Translations 