In 150 BC, the Greek Hippalos discovered strong monsoons that allowed seafaring using improved Roman wooden ships from the Red and Arab Seas to the spice coast of modern Kerala and back. This enabled trade in what made the subcontinent as rich as silk-home China. Herbal products like peppers, ginger, cardamom and other conservation - and seasoning ingredients, worth up to their weight in gold, plus gems, paid mainly in metals and wine. India's fertile south conserves the Ancient Tamil language and metropolitan capital then, Manduarai. North of the Himalaya, the Kushan tribes formed a now forgotten empire, based on Merw (Turkmenistan), which opened the Silk Route, the main land trade.
—KGF Vissers