Iron was used in India by about 500 B.C and had been known as early as 900 B.C. In Hindi it is called Chumbak (kissing stone) and Maqnatees in Urdu & Persian. In ancient days, foreign traders and travelers visited Malabar Coast. The most important of them were the Greeks, Romans, Chinese and Arabs. A large no. of coins of the first four centuries of A.D. in the Trichur Museum indicates the trade that existed between the Romans and Malabar. Indian medicinal spice pepper was one of the most important items of trade.

Vedic texts show that the ancient people of our land did undertake naval expeditions and travel to distant places through sea routes well known to them. All evidences reveal that ships were sent to foreign countries for trade, and sea routes were known even during the vedic days. Multi-oared boats were used in these expeditions. Sixteen types of winds, helpful for sea navigation were known to ancient people. Since sailing was dependent on winds, they were carefully observed and studied. The advancement of astronomical study also facilitated the activities across the seas. During earlier periods, sailors made use of crows on board to find the direction in which land was situated.

Two Indian astronomers of great repute Aryabhatta and Varahamihira, having accurately mapped the positions of celestial bodies, developed a method of computing a ship’s position from stars. Remarkable progress in astronomy was achieved during this period. Art of oceanic navigation by rough and ready computation of position of ship from known stars was introduced by the then great astronomers Aryabhatta and Varahamihira. It is of immense interest to note that plotting of starry sky had been accomplished even before the discovery of the magnetic compass.

“A crude forerunner of modern magnetic compass was being used around fourth or fifth century A.D. called “Matsya Yantra”. It comprised an iron fish that floated in a vessel of oil, pointing north. According to Bombay Gazetteer: The Hindu Compass was an iron fish that floated in a vessel of oil and pointed to the north. Even in the modern days, we have liquid filled compasses.

Jacques de Vitry in his “History of the Kingdom of Jerusalem “ (1218 A.D.) referred to the use of the compass in India. An Arabic manual of mineralogy (1252 A.D.) said that Indian seamen steered by an iron fish floating in a bowl of oil.

In the temples of “Tadiparti” Ananatpur district, A..P., fish symbols are depicted to indicate falling of water while Brahma is cleaning one leg of Lord Vishnu (while the other leg being cleaned by Bali chakravarthi) – this implies that fish is shown to indicate something related to water or to show water itself on the stone architecture. Therefore, we can say that the “Matsya-Yantra” was first used in Sea navigation. Later on, it was introduced to the other fields.

Whether it is a dwelling house or temple, as per vaastu-sastra, the Indian science of architecture, ‘building the structure to cardinal points’ is very important, this is called “Dik-sadhana”. A wooden gnomon known as “sanku” is used for finding cardinal directions in the traditional method. All the classical texts of Vastu-Sastra give detailed procedure for Dik-sadhana. However, nowadays, we all use modern day “magnetic compass” to find cardinal directions as well as corners, which is very easy to use. Presently, everybody prefers to use modern day compass even for vastu purposes. In fact, the exact period when it was introduced in the field of Vastu-Sastra is not correctly known.