Sundial

Around the time the Toa were searching for their Kanohi, Onu-Matoran miners discovered a large sundial buried in a seemingly impenetrable rock layer in an Onu-Wahi mine. While exploring, Takua joined the prospectors examining the sundial. One of them asked him to deliver a message to an astrologer he knew. The astrologer determined that when the shadow from the sundial's gnomon hit the four o'clock position, something would happen. She then gave Takua a gnomon she had found some time ago, which she suspected went with the sundial. Sure enough, the gnomon fit, and when Takua shined a lightstone on it so that it indicated four o'clock, the sundial opened, revealing a passage through the rock layer with a gold Kanohi Hau at the bottom. The Hau later disappeared mysteriously.

Much later, after the Matoran had returned to Metru Nui and the Toa were following a list of tasks needed to restore the universe to working order, a strange voice told Lewa to return to Mata Nui and retrieve the sundial, which he did.