The ancient Hindus have created a massive literature which they transmitted orally for several millennia—to facilitate memorization, the source material was kept minimal and each sutra (aphorism) was designed to serve as a mnemonic device. The Indus Script has been dated to 3000 B.C., but literary writing began in the 5th century B.C.; the oral tradition has, however, continued till the 15th century A.D. Most scholars believe that the oral transmission has been accurate and there is no reason for us to question the accuracy of the ancient texts. The Rigveda, the oldest of the four Vedas, is a collection of ten books consisting of 1,028 hymns with 10,600 verses. The Samaveda is larger than the Rigveda since it explains the changes that the verses in the Rigveda undergo when they are chanted or used in ritual. The Yajurveda too is larger than the Rigveda because it consists of a number of schools, which articulate their differing viewpoints. The Atharvaveda consists of almost 6000 verses. Then there are the Puranas which describe the ancient myths, legends, and other traditional lore—the eighteen Great Puranas (Mahapuranas) and eighteen Minor Puranas (Upa Puranas) consist of approximately 400,000 verses. The Mahabharata consists of 1.8 million words, which makes it ten times the combined length of the Iliad and the Odyssey. Other than the four Vedas, thirty-six major and minor Puranas, the Mahabharata, there are several other religious, mythological, and philosophical texts that the ancient Hindus have created—theirs could be the largest oral tradition in history.