... has by heart most of the glorious Quran ... and every day he recites two chapters in the presence of (Quran) memorizers and no mistake is made. He knows (Arabic) grammar well and he writes Arabic composition extremely well, and like-wise he is well posted in canon law; he has knowledge of logic, rhetoric, and elocution, and likewise of the Elements (of Euclid), and he himself cultivates the branches of mathematics, and this has reached the extent that one day while riding he wanted to determine the date, which was a Monday of [the month of] Rajab, between the fifth and the tenth in the year eight hundred and eighteen (A. H.), as to what day it was of the (astronomical) season of the year. From these very given data, by mental computation, and from horseback, he determined the true longitude of the sun (correct) to degrees and minutes. When he came back he asked this humble servant about it. Truly, since in mental computation the quantities must be retained by memory and others determined, and there is a limit to one's strength of retention, he (i.e. I) was not able to extract it to degrees and minutes, but contented myself with degrees.