top, peak, summit, upset
顚 centers on the highest point or peak, both physically (summit, top) and metaphorically (an upset that turns things over). The upset sense likely extends from the idea of something being overturned or flipped to its peak state.
顚 combines 眞 (true, real) with 頁 (head). The original idea likely relates to the top of the head or the crown, extending to any peak or summit. The upset meaning may come from the notion of being turned on one's head.
The left side 眞 suggests something solid and real, while the right side 頁 means head. Imagine the very top of a real head—the crown—as the summit. When that summit is upset, everything flips over.
For テン, picture the number ten (テン) sitting at the very peak of a mountain: ten -> テン, and it marks the top.