Emperor Kangxi (1654 - 1722, reigned 1661 - 1722) was an avid learner. He learned mathematics and astronomy from the Jesuit missionaries who visited Peking (Beijing). The following excerpt is from a diary of Emperor Kangxi called the Tingxun Geyan (《庭训格言》, Familial Admonitions).
You all only know that I am good at mathematics but you do not know why I study mathematics. When I was young, the Han officials at the Imperial Bureau of Astronomy did not get along with the Westerners. They accused each other to the point that someone could have been executed! Later, Yang Guangxian and Tang Ruowang (Johann Adam Schall von Bell)* predicted the sun's shadow in front of the Nine Ministers outside the Meridian Gate, and not one of them understood the calculation methods. I then thought, if I don't know, how can I judge who is right and who is wrong? This is why I put great effort in learning mathematics.
*应该是南怀仁。Should be Ferdinand Verbiest (Nan Huairen).
 朕 zhèn：皇帝的人称代词。Personal pronoun of the Chinese emperor.
 钦天监 qīn tiān jiàn：明清两朝观察天文、天象、历法的机构。Imperial Bureau of Astronomy.
 午门 wǔ mén：紫禁城的正门。Meridian Gate (main gate of the Forbidden City).
 九卿 jiǔ qīng：中国古代朝廷的九个高级官职。Nine high-ranking officials of Imperial China.