On page 73, describes how Meg feels when she accidentally touches down on a two-dimensional planet.

They all then begin to disintegrate again, and Meg holds Calvin’s hand. A mistake is made, however, and Meg finds herself feeling crushed and flat. She can’t expand her lungs and her mind won’t work correctly either. She hears the words “Oh, no! We can’t stop here! This is a two-dimensional planet...” and suddenly Meg is thrown through time and space once again where she regains her sense of life. Charles Wallace is angry at the women for making a mistake that almost killed them all, but they all laugh because they so rarely make such mistakes and didn’t think about the physical nature of the children.