The Indus Valley's Bronze Age civilisation may have developed the world's first sophisticated system of wage labour, financial exchange and measurement, a Canadian mathematician has discovered.

According to a new study of clay pots and ceramic tablets discovered almost 70 years ago in Harappa, now in Pakistan, the people of the Indus Valley had a detailed system of commodity value, weights and measures.

Dr Bryan Wells, a researcher based at India's Institute of Mathematical Sciences, told The Daily Telegraph he had begun work on his thesis ten years ago when he first saw photographs of the clay pots with markings which appeared to be in proportion to their relative size.

But he was not able to test his thesis until he visited New Delhi earlier this month where the original pots are stored in one of the city's Mughal era forts. The three pots each had different markings, the smallest with a 'V' to indicate 'measure' and three long strokes. The medium vessel had six strokes and the largest had seven.

When he measured them he found they were in proportionate capacity: 3:6:7.

The inscriptions on the pots matched those on bas relief ceramic tablets which he believes are tokens of exchange for fixed measures of grain or other commodities.

The size of the pots - the largest is 2.7 metres in circumference, and contains 65 litres - indicates an organised system of exchange for large scale transactions, he said.

The bas-relief tablets are "definitely some kind of exchange token. These pots are more than one metre wide. You're not going to be carrying them around. The chits or tablets have representative value and they are being used in an economic context," he said.

In his paper, "Indus Weights and Measures," to be published in the archeological journal Antiquity next year, Dr Wells suggests the tablets may be the equivalent of 'wage slips' or credits for work representing fixed volumes of food.

"It is possible that wages were paid with grains dispersed from a centralised storage facility or in the case of incised tablets material for construction projects and other short-term projects," he wrote.

Although older coins and ingots have been discovered from the Mesopotamia, but Dr Wells' findings amount to a more detailed decoding of an ancient value system.