《抱朴子·内篇·论仙》
要想使这些人一定相信这些仙人的存在，好比让蚊子牛虻背起大山，和井底的蛤蟆谈论大海。
望使必信，是令蚊虻负山，与井蟆论海也。
If you want these people to believe in the existence of these immortals, it would be like asking mosquitoes and gadflies to carry mountains and talking to a frog in a well about the ocean.