" Modern scientists now believe that there are seven broad forms of energy—mechanical, heat, chemical, radiant, electrical, sound, and nuclear. It is my reasoned guess that the ancient yogis knew this. They also knew that each of these could be broken into seven constituent elements! It’s impossible to understand how they knew this, but they did. Even their most important and exalted river—the Sarasvati—was part of the Saptasindhu, the seven rivers. Vedic knowledge was derived from the Saptarishi—the seven sages. Even Dwarka was the embodiment of Saptadweep—the seven islands. "

― Ashwin Sanghi , The Krishna Key