Volume One of 'The Great Pyramid Passages and Chambers' by John and Morton Edgar was published in 1910.
Their work followed on from earlier investigators such as John Taylor and Piazzi Smyth. They all saw the Great Pyramid as a symbolic representations of 'Gods' message.
They traveled to Egypt in 1906 to confirm the work of the American writer CT Russell who linked the measurements of the various passages to biblical texts and prophecies.
They returned having in their words "discovered fresh beauties in the symbolic and prophetic teaching of this marvelous structure."
The main interest of the book today are the numerous black and white photographs which record features of the Great Pyramid before the modern cleaning and restoration which has masked many features that the brothers recorded.
Some areas, such as the Grotto, are rarely photographed even today and their record is still one of the best available.
They had some of the subterranean areas cleared of debris and thus measured some features not accessible to earlier researchers such as Petrie.