The Egyptian priest Manetho wrote a history of Egypt during the 3rd century BC known as the "Aegyptiaca". Manetho's work has not survived to this day and is only known to us via three later writers who quoted from it. Unfortunately, these three sources are exceedingly difficult to work with. For example, they often contradict each other, as is the case for the two ancient historians – Sextus Julius Africanus and Eusebius of Caesarea – who quote from the section of the "Aegyptiaca" regarding the Seventh and Eighth Dynasties. Africanus claims that the 7th Dynasty consisted of 70 kings that ruled during a period of seventy days in Memphis, and the 8th Dynasty consisted of 27 kings who reigned for 146 years. However, Eusebius records that during the 7th Dynasty five kings ruled over seventy five days, and the 8th Dynasty includes five kings who ruled for 100 years. Seventy kings in seventy days is usually considered the correct version of Manetho concerning the Seventh Dynasty, but likely not a factual account of history. Rather, this is interpreted to mean that the pharaohs of this period were extremely ephemeral, and the use of seventy may be a pun on the fact that this was Manetho's Seventh Dynasty. Because Manetho does not provide actual historical data on this period and no archeological evidence for the Seventh Dynasty has emerged, many Egyptologists have argued that this dynasty is fictitious. Concerning the Eighth Dynasty, it is now widely agreed that Manetho's estimate for its duration is a very substantial overestimation of the reality.