Mozi, dated to the 4th century BC, traditionally ascribed to and named for Mozi (circa 470 BC-circa 391 BC), a Chinese philosopher and the founder of Mohist School of Logic. These writings explain how the image in a "collecting-point" or "treasure house" is inverted by an intersecting point (pinhole) that collects the (rays of) light. Light coming from the foot of an illuminated person were partly hidden below (i.e., strike below the pinhole) and partly formed the top of the image. Rays from the head were partly hidden above (i.e., strike above the pinhole) and partly formed the lower part of the image. Another early account is provided by Greek philosopher Aristotle (384–322 BC), or possibly a follower of his ideas. Similar to the later 11th-century Arab scientist Alhazen, Aristotle is also thought to have used camera obscura for observing solar eclipses. Camera obscura is touched upon as a subject in Aristotle's work Problems – Book XV, asking: and further on: Many philosophers and scientists of the Western world pondered this question before it was accepted that the circular and crescent-shapes described in the "problem" were pinhole image projections of the sun. Although a projected image has the shape of the aperture when the light source, aperture and projection plane are close together, the projected image has the shape of the light source when they are farther apart. In his book Optics (circa 300 BC, surviving in later manuscripts from around 1000 AD), Euclid proposed mathematical descriptions of vision with "lines drawn directly from the eye pass through a space of great extent" and "the form of the space included in our vision is a cone, with its apex in the eye and its base at the limits of our vision." Later versions of the text, like Ignazio Danti's 1573 annotated translation, would add a description of the camera obscura principle to demonstrate Euclid's ideas. 500 to 1000: Earliest experiments, study of light In the 6th century, the Byzantine-Greek mathematician and architect Anthemius of Tralles (most famous as a co-architect of the Hagia Sophia) experimented with effects related to the camera obscura. Anthemius had a sophisticated understanding of the involved optics, as demonstrated by a light-ray diagram he constructed in 555 AD. In the 10th century Yu Chao-Lung supposedly projected images of pagoda models through a small hole onto a screen to study directions and divergence of rays of light.