Brick sizes were in a perfect ratio of 4:2:1, and the decimal system was used. Weights were based on units of 0.05, 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, and 500, with each unit weighing approximately 28 grams. In addition, they evolved new techniques in metallurgy, and produced copper, bronze, lead, and tin. The engineering skill of the Harappans was remarkable, especially in building docks after a careful study of tides, waves, and currents.
The Harappans were well versed in astronomy. It is clearly evident from the excavations. The straight streets of the Indus cities were oriented towards the basic directions, which presupposes astronomical observations and the use of the sun-stick. The Aryans in India adopted the star-calendar used by the Vedic ritualists. But there are no references to it in the Avesta or in the oldest books of the Rigveda. On the other hand, astronomical evidence dates the compilation of this calendar at around the 23rd century B.C., when the Indus civilisation flourished at its peak. Linkages between ancient Harappan scripts and latter Vedic texts suggest that Harappan priest-astronomers tracked progress of Mercury, Venus and Saturn, and most likely all of the planets.