Sorry if I am sceptical but I don't really believe your claim that you were able to obtain a sound working knowledge of calculus from the Principia.
For one thing, Newton barely makes use of calculus in the textbook and instead opts for geometric methods. And even with that, he is not rigorous at all because rigor hadn't been discovered yet. I wouldn't even put it on the same level as modern textbooks since so much had yet to be discovered about calculus.
I would not recommend the Principa to anyone except for historical interest. Everything in that book has been said more concisely by other people in the three hundred years since it was published.
For one thing, Newton barely makes use of calculus in the textbook and instead opts for geometric methods. And even with that, he is not rigorous at all because rigor hadn't been discovered yet. I wouldn't even put it on the same level as modern textbooks since so much had yet to be discovered about calculus.
I would not recommend the Principa to anyone except for historical interest. Everything in that book has been said more concisely by other people in the three hundred years since it was published.