Final answer:
Einstein fondly called Euclid's 'Elements of Geometry' the 'holy little geometry book,' acknowledging its significant impact on his development of both the special and general theories of relativity.
Step-by-step explanation:
Einstein referred to 'Elements of Geometry' by the ancient Greek mathematician Euclid as “the holy little geometry book”. Throughout his scientific career, Einstein relied on his deep physical intuition and the fundamental principles laid out in this book. As a young student, he was profoundly influenced by the logical structure and clear, demonstrable proofs found within its pages, which fostered his appreciation for geometric thinking and profoundly shaped his later work, including the development of the special theory of relativity and the general theory of relativity. This geometry book can be considered a foundational component in his groundbreaking contributions to our understanding of space, time, motion, and gravity.