Notebook.

Isaac Newton's mother took him out of school so he could help run the farm believing that, since he was good with his hands and had a quick mind, he would be a very capable manager. But because he was indeed quick with his mind, Isaac was an absolutely terrible manager.
When he was supposed to be watching the sheep or cows, Isaac was curled up under a shady hedge with a book. When he was supposed to be taking the produce to market, he was down in the fields jumping this way and that, trying to determine by the lengths of his jumps, what the force of the wind was. When he should have been feeding the chickens, he was jotting down thoughts in his notebook. At the front of the notebook he'd proudly written 'Isaac Newton owns this book.'
It included, among other things, his formula for making chalk, recipes for purging the head and making the brain clear, a phonetic alphabet, methods for making gold ink, magic tricks, and astronomical observations. And while he wrote all these ideas, the cattle were wandering onto the neighbor's land and the hens were still waiting for their eggs to be collected.