The Eleventh Book relates to penance and expiation. In this book is mentioned the remarkable rite which consists in drinking the fermented juice of the moon-plant (or acid asclepias) with religious ceremonies. This Hindu sacrament began in the Vedic age, and the Sanhita of the Sama-Veda consists of hymns to be sung at the moon-plant sacrifice.[51] This ceremony is still practised occasionally in India, and Dr. Hang has tasted this sacred beverage, which he describes as astringent, bitter, intoxicating, and very disagreeable.[52] It is stated by Manu that no one has a right to drink this sacred juice who does not properly provide for his own household. He encourages sacrifices by declaring that they are highly meritorious and will expiate sin. Involuntary sins require a much lighter penance than those committed with knowledge. Crimes committed by Brahmans require a less severe penance than those performed by others; while those committed against Brahmans involve a much deeper guilt and require severer penance. The law declares:-- "From his high birth alone a Brahman is an object of veneration, even to deities, and his declarations are decisive evidence." "A Brahman, who has performed an expiation with his whole mind fixed on God, purifies his soul." Drinking intoxicating liquor (except in the Soma sacrifice) is strictly prohibited, and it is even declared that a Brahman who tastes intoxicating liquor sinks to the low caste of a Sudra. If a Brahman who has tasted the Soma juice even smells the breath of a man who has been drinking spirits, he must do penance by repeating the Gayatri, suppressing his breath, and eating clarified butter. Next to Brahmans, cows were the objects of reverence, probably because, in the earliest times, the Aryan race, as nomads, depended on this animal for food. He who kills a cow must perform very severe penances, among which are these:-- "All day he must wait on a herd of cows and stand quaffing the dust raised by their hoofs; at night, having servilely attended them, he must sit near and guard them." "Free from passion, he must stand while they stand, follow when they move, and lie down near them when they lie down." "By thus waiting on a herd for three months, he who has killed a cow atones for his guilt."