<P> Obelisks were a prominent part of the architecture of the ancient Egyptians, who placed them in pairs at the entrances of various monuments and important buildings, such as temples . In 1902, Encyclopædia Britannica wrote, "The earliest temple obelisk still in position is that of Senusret I of the XIIth Dynasty at Heliopolis (68 feet high)". The word "obelisk" is of Greek rather than Egyptian origin because Herodotus, the great traveler, was the first writer to describe the objects . Twenty - nine ancient Egyptian obelisks are known to have survived, plus the unfinished obelisk being built by Hatshepsut to celebrate her sixteenth year as pharaoh . It broke while being carved out of the quarry and was abandoned when another one was begun to replace it . The broken one was found at Aswan and provides the only insight into the methods of how they were hewn . The obelisk symbolized the sky deity Ra and during the brief religious reformation of Akhenaten, was said to be a petrified ray of the Aten, the sun disk . It is hypothesized by New York University Egyptologist Patricia Blackwell Gary and Astronomy senior editor Richard Talcott that the shapes of the ancient Egyptian pyramid and Obelisk were derived from natural phenomena associated with the sun (the sun - god Ra being the Egyptians' greatest deity). It was also thought that the deity existed within the structure . The Egyptians also used pillars extensively . </P> <P> It is unknown whether the Ancient Egyptians had kites, but a team led by Maureen Clemmons and Mory Gharib raised a 5,900 - pound, 15 - foot (4.6 m) obelisk into vertical position with a kite, a system of pulleys, and a support frame . Maureen Clemmons developed the idea that the ancient Egyptians used kites for work . Ramps have been reported as being widely used in Ancient Egypt . A ramp is an inclined plane, or a plane surface set at an angle (other than a right angle) against a horizontal surface . The inclined plane permits one to overcome a large resistance by applying a relatively small force through a longer distance than the load is to be raised . In civil engineering the slope (ratio of rise / run) is often referred to as a grade or gradient . An inclined plane is one of the commonly - recognized simple machines . Maureen Clemmons subsequently led a team of researchers demonstrating a kite made of natural material and reinforced with shellac (which according to their research pulled with 97% the efficiency of nylon), in a 9 mph wind, would easily pull an average 2 - ton pyramid stone up the 1st two courses of a pyramid (in collaboration with Cal Poly, Pomona, on a 53 - stone pyramid built in Rosamond, CA). </P> <P> The Ancient Egyptians had knowledge to some extent of sail construction . This is governed by the science of aerodynamics . The earliest Egyptian sails were simply placed to catch the wind and push a vessel . Later Egyptian sails dating to 2400 BCE were built with the recognition that ships could sail against the wind using the lift of the sails . Queen Hatshepsut oversaw the preparations and funding of an expedition of five ships, each measuring seventy feet long, and with several sails . Various others exist, also . </P> <Ul> <Li> <P> Egyptian ship with a loose - footed sail, similar to a longship . From the 5th dynasty (around 2700 BC) </P> </Li> <Li> <P> Model ship from the Old Kingdom (2686--2181 BC) </P> </Li> <Li> <P> Stern - mounted steering oar of an Egyptian riverboat depicted in the Tomb of Menna (c. 1422--1411 B.C.) Note that the sail is stretched between yards . </P> </Li> <Li> <P> Loading Egyptian vessels with the produce of Punt . Shows folded sails, lowered upper yard, yard construction, and heavy deck cargo . </P> </Li> </Ul>

Who used to travel the nile river with wind power
find me the text answering this question