Trishool that Shiva holds - central part is the sushumna, right is the Pingala and left is the Ida nadi. When the Yogi symbolises the Trishool, it’s the spinal cord, the sushumna. And there is a damru tied as well, which is the internal sound that you hear when Ida - Pingala is balanced, and your energy is rising in the Sushumna, through the middle.