This quote emphasizes the importance of understanding foundational principles before attempting to create or innovate. In this context, "The Book of the science of Mechanics" symbolizes the fundamental knowledge and principles of mechanics, while "the Book of useful inventions" represents the application of these principles in creating practical and useful inventions.

Da Vinci is suggesting that a deep understanding of the basic principles of any field is a prerequisite to making significant contributions or innovations in that field. This is because without a firm grasp of the basics, any attempts to innovate or create are likely to be misguided or ineffective.

Applying this to today’s world, one could argue that it’s crucial to master the basics before trying to innovate or create. For example, in the tech industry, before one can develop a groundbreaking app or software, one must first understand the principles of coding and software development.

In terms of personal development, this quote could be interpreted as a call to focus on mastering foundational skills and knowledge before attempting to reach more advanced levels. For instance, if you’re learning a new language, it’s important to first understand the basics of grammar and vocabulary before trying to engage in complex conversations or write sophisticated essays.

Overall, this quote highlights the importance of building a strong foundation of knowledge and skills, as it is this foundation that enables us to create, innovate, and reach higher levels of achievement.