According to the Tianguan shu of "Shiki" (the Chinese Historical records), Kengyu at the time was Gyushuku and current Kengyu, namely Altair, is a star belonging to the constellation called Kako (drum of the Milky Way).
前漢の『史記』天官書を見るとかつての牽牛は牛宿のことであり、現在の牽牛すなわちアルタイルは河鼓（天の川の太鼓）と呼ばれる星座の一星である。