As for what He عليه السلام, may Allah سبحانه وتعالى have mercy on him, mentioned regarding determining the sun's zenith (‘zawal’) using the astrolabe and the geometrical circle, the reference in that matter is to the experts, and it is not derived from transmitted reports (‘athar’). As for determining it by means of the upright stick (‘al-’ud al-mansub’):
Commentary #7