Lying on its back, the turtle was tight in its shell for a long time. But at last its legs waved in the air, reaching for something to pull it over.
– John Steinbeck
The Grapes of Wrath, Chapter 3. After a truck flips over the turtle a threatens its survival, the animal lies upside down in a vulnerable position. The short journey across the highway has become a dangerous one. Still the turtle refuses to give up and is determined to make that journey.