What does this approx. 300-year-old Korean text by Choi Seok-Jeong say? This image comes from the paper https://arxiv.org/pdf/1812.02202.pdf:



It's an old Korean orthogonal Latin square attributed to Choi Seok-Jeong, in the book Koo-Soo-Ryak.  It's of historical interest, since it predates Euler, and he's usually the one attributed to inventing Latin squares.  It's probably in the ballpark of 300 years old.

The orthogonal Latin square is simple enough (they're basically today's numbers), and I can partially read some of the characters, e.g., it begins 九九母？？宫, but I'm really struggling to recognize most of the other characters.  I asked some Chinese colleagues and they can recognize more of the characters, but also struggle.
Here is my transcription into an ROC/HK standard character set.

《九九母數變宮陽圖》
從？皆得九十數總積八百一十母數
本宮圖即甲編母數名圖此圖自本
宮而一變
橫看從看
九數無一
重複者〇
以下四圖
係新定


I have a feeling the second character ？ is「衡」.
Please be wary of phonetic loans. For example,「從」might be better off being interpreted as「縱」. With the above, you have the two characters as「縱衡」(vertical and horizontal).