There is a story in buddhism called “The One-Eyed Turtle and the Floating Log”. The following quote is a description of this orally transmitted story from the Lotus Sutra (teachings of Shakyamuni Buddha). The story is used to describe the rarity of being born as a human being (and encountering the teachings of the buddha):
“Eighty thousand yojanas down, on the bottom of the ocean, lives a large sea creature called a turtle. He has neither limbs nor flippers. His belly is as hot as heated iron, but the shell on his back is as cold as the Snow Mountains. What this turtle yearns for day and night, morning and evening—the desire he utters at each moment—is to cool his belly and warm the shell on his back.
The red sandalwood tree is regarded as sacred and is like a sage among people. All other trees are regarded as ordinary trees and are like foolish people. The wood of this sandalwood tree has the power to cool the turtle’s belly. The turtle longs with all his might to climb onto a sandalwood log and place his belly in a hollow there in order to cool it, while exposing the shell on his back to the sun in order to warm it. According to the laws of nature, however, he can rise to the ocean’s surface once every thousand years. But even then it is difficult for him to find a sandalwood log. The ocean is vast, while the turtle is small, and floating logs are few. Even if he finds some floating logs, he seldom encounters one of sandalwood. And even when he is fortunate enough to find a sandalwood log, it rarely has a hollow the size of his belly. If [the hollow is too large and] he falls into it, he cannot warm the shell on his back, and no one will be there to pull him out. If the hollow is too small and he cannot place his belly in it, the waves will wash him away, and he will sink back to the ocean’s floor.
Even when, against all odds, the turtle comes across a floating sandalwood log with a hollow of the right size, having only one eye, his vision is distorted, and he sees the log as drifting eastward when it is actually drifting westward. Thus the harder he swims in his hurry to climb onto the log, the farther away he goes. When it drifts eastward, he sees it as drifting westward, and in the same way, he mistakes south for north. Thus he always moves away from the log, never approaches it.”
- From the Writings of Nichiren Daishonin, p.958