The original textbook of geometry was written approximately 2300 years ago by Euclid of Alexandria, an Egyptian-Greek mathematician. It can still be used as a textbook today, and was in frequent use in classrooms as late the 20th century. That is not something you can say for most books--that it will still be useful in the classroom 23 centuries after publication. That is the lasting power of mathematics.
Here is the original text in Greek, along with a side-by-side English translation, from the University of Texas.
http://farside.ph.utexas.edu/Books/Euclid/Elements.pdf
Here is the original text in Greek, along with a side-by-side English translation, from the University of Texas.
http://farside.ph.utexas.edu/Books/Euclid/Elements.pdf