"The beast that thou sawest was, and is not; and shall ascend out of the bottomless pit, and go into perdition" (Rev. 17.8).

The beast that "was" was Nero, "is not" at the time of John's writing because Nero had died, and "shall ascend out of the bottomless pit."

"And the beast that was, and is not, even he is the eighth, and is of the seven, and goeth into perdition" (Rev. 17.11).

We also discover this 1st beast, the Antichrist, is "the eighth" and is "of the seven".

"And there are seven kings: five are fallen, and one is, [and] the other is not yet come; and when he cometh, he must continue a short space" (Rev. 17.10).

This king who is to come is the seventh [Prince William], but he is here only a short while, so he wouldn't be the Antichrist who is the eighth. "The one is" can't be the Antichrist because at the time of John's writing he "is not". So the eighth must be one of the five. These five are clearly the five fallen Caesars. Which one is the eighth? Obviously Nero for only Nero's name in Aramaic, equals 666 (Neron Kaisar).

"Here is wisdom. Let him that hath understanding count the number of the beast: for it is the number of a man; and his number [is] Six hundred threescore [and] six" (Rev. 13.18).

Ergo, "The beast [Antichrist] that thou sawest was, and is not; and shall ascend out of the bottomless pit, and go into perdition" (Rev. 17.8).