Although he said in his afterword to "Tokushi Yoron" that 'these three books above are drafts of lecture notes from when I gave lectures on ancient and modern times in the presence of my master from spring to summer in the second year of Shotoku (Japan),' it is known from the afterword in kanbun (Sino-Japanese) that in fact the original draft was completed before then.
『読史余論』の自跋には「右三冊ハ正徳(日本)二年春夏之間、座ヲ賜テ古今ヲ論ジ申セシ時ノ講章ノ草本也」とあるが、実際に稿本が完成されたのはそれ以前であることが漢文の自跋によって知られる。