How do I verify the rotation matrix I receive after camera calibration?

Hi guys,

I am currently working on the intrinsic and extrinsic calibration of cameras using OpenCV. I use cv. solvePNP() to get the rotation and translation of a camera. I can verify the translation with a tape measure. However, it is difficult for me to verify the rotation, because I think a triangle ruler gives too large measurement errors. Is there a better method to verify the rotation matrix?