Megastenes (350 BC - 290 BC), Greek traveller and geographer wrote about castes in his "Indika
The whole population of India is divided into seven castes, of which the first is formed by the collective body of the Philosophers, which in point of number is inferior to the other classes, but in point of dignity preeminent over all. For the philosophers, being exempted from all public duties, are neither the masters nor the servants of others. They are, however, engaged by private persons to offer the sacrifices due in lifetime, and to celebrate the obsequies of the dead: for they are believed to be most dear to the gods, and to be the most conversant with matters pertaining to Hades. In requital of such services they receive valuable gifts and privileges. To the people of India at large they also render great benefits, when, gathered together at the beginning of the year, they forewarn the assembled multitudes about droughts and. wet weather, and also about propitious winds, and diseases, and other topics capable of profiting-the hearers. Thus the people and the sovereign, learning beforehand what is to happen, always make adequate provision against a coming deficiency, and never fail to prepare beforehand what will help in a time of need. The philosopher who errs in his predictions incurs no other penalty than obloquy, and he then observes silence for the rest of his life.
The second caste consists of the Husbandmen, who appear to be far more numerous than the others. Being, moreover, exempted from fighting and other public services, they devote the whole of their time to tillage; nor would an enemy coming upon a husbandman at work on his land do him any harm, for men of this class, being regarded as public benefactors, are protected from all injury. The land, thus remaining unravaged, and producing heavy crops, supplies the inhabitants with all that is requisite to make life very enjoyable. The husbandmen themselves, with their wives and children, live in the country, and entirely avoid going into town. They pay a land-tribute to the king, because all India is the property of the crown, and no private person is permitted to own land. Besides the land-tribute, they pay into the royal treasury a fourth part of the produce of the soil.
The third caste consists of the Neatherds and Shepherds and in general of all herdsmen who neither settle in towns nor in villages, but live in tents. By hunting and trapping they clear the country of noxious birds and wild beasts. As they apply themselves eagerly and assiduously to this pursuit, they free India from the pests with which it abounds,--all sorts of wild beasts, and birds which devour the seeds sown by the husbandmen.
The fourth caste consists of the Artizans. Of these some are armourers, while others make the implements which husbandmen and others find useful in their different callings. This class is not only exempted from paying taxes, but even receives maintenance from the royal exchequer.
The fifth caste is the Military. It is well organized and equipped for war, holds the second place in point of numbers, and gives itself up to idleness and amusement in the times of peace. The entire force--men-at-arms, war-horses, war-elephants, and all--are maintained at the king's expense.
The sixth caste consists of the Overseers. It is their province to inquire into and superintend all that goes on in India, and make report to the king, or, where there is not a king, to the magistrates.
The seventh caste consists of the Councillors and Assessors,--of those who deliberate on public affairs. It is the smallest class, looking to number, but the most respected, on account of the high character and wisdom of its members; for from their ranks the advisers of the king are taken, and the treasurers, of the state, and the arbiters who settle disputes. The generals of the army also, and the chief magistrates, usually belong to this class.
Such, then, are about the parts into which the body politic in India is divided. No one is allowed to marry out of his own caste, or to exercise any calling or art except his own: for instance, a soldier cannot become a husbandman, or an artizan a philosopher.
Of the Manners of the Indians.
The Indians all live frugally, especially when in camp. They dislike a great undisciplined multitude, and consequently they observe good order. Theft is of very rare occurrence. Megasthenes says that those who were in the camp of Sandrakottos [Chandragupta], wherein lay 400,000 men, found that the thefts reported on any one day did not exceed the value of two hundred drachmae, and this among a people who have no written laws, but are ignorant of writing, and must therefore in all the business of life trust to memory. They live, nevertheless, happily enough, being simple in their manners and frugal. They never drink wine except at sacrifices. Their beverage is a liquor composed from rice instead of barley, and their food is principally a rice-pottage. The simplicity of their laws and their contracts is proved by the fact that they seldom go to law. They have no suits about pledges or deposits, nor do they, require either seals or witnesses, but make their deposits and confide in each other. Their houses and property they generally leave unguarded. These things indicate that they possess good, sober sense; but other things they do which one cannot approve: for instance, that they eat always alone, and that they have no fixed hours when meals are to be taken by all in common, but each one eats when he feels inclined. The contrary custom would be better for the ends of social and civil life.
Source: Project South Asia