I have collected math books from the early 1700s until the late 1900s—and spent tons of my own money on them. There are great singular books, especially Euler’s, but there are none, which give you a synopsis and enough practice. 

Here are two authors, which will do this:

Max Planck’s five-volume “Einfuehrung in die Theoretische Physik” (Introduction to Theoretical Physics) which started appearing in and after WW1 are very very sophisticated exercise books requiring the mathematics of the time. Planck expects the reader to calculate through the books. He guides the reader, but the reader has to contribute. The question is where to find the mathematical knowledge. There was a student of the famous David Hilbert, who graduated under his guidance with the 1914 Dissertation “Theoretische Behandlung der Erscheinungen in Verduennten Gasen” (Theoretical Treatment of the Phenomena in Rarified Gases). The student (Bernhard Baule) in and after WW2, published a sequence of excellent little books “Die Mathematik des Naturforshers und Ingenieurs” (Mathematics for Scientists and Engineers, 7 volumes with a total of 720 pages) which give you exactly the knowledge to deal with Planck’s introduction without too much effort. Planck is the gold standard of theoretical physics. It is possible that Baule wrote his books to make Planck more accessible. To give you an impression of Baule: The series begins with a book on calculus (150 pages), which beats every thick modern calculus book. The whole series will give you an overview of mathematics, which you will not receive in any of today’s math departments.

After going through Baule and Planck, you will be able to deal with Einstein.

SCHOOLBOOKS OF THE TIME (prior to WW1)

I recommend:

Author: Professor Dr. Chr.  Schmehl

Publisher:Emil Roth, Giessen, Germany

Titles:

1) Lehrbuch der Arithmetik und Algebra (Erster Teil)

2) Lehrbuch der Arithmetik und Algebra (Zweiter Teil)

3) Lehrbuch der ebenen Geometrie für höhere Lehranstalten

4) Lehrbuch der ebenen Trigonometrie für höhere Lehranstalten

Optional:

5) Die Algebra und algebraische Analysis mit Einschluβ einer elementaren Theorie der Determinante (Can be considered as a third volume of 1. And 2.)

Remark: The quality of these books is surprising.