"Traité des propriétés projectives des figures" is a foundational work in projective geometry, authored by Gustavus E. M. de la Vallée Poussin in the early 20th century. The book explores the properties of geometric figures that remain invariant under projection, emphasizing the relationships between points, lines, and planes in a projective space. The treatise delves into concepts such as duality and the significance of perspective in geometry. It serves as a critical reference for mathematicians and students interested in understanding the principles of projective geometry, which has applications in various fields, including computer graphics and art.