The Silent Stones by Diana Cooper

(From goodreads.com)

Handed a sacred scroll from Atlantis by a dying Tibetan monk, Marcus, Joanna and Helen are propelled into adventure as they race to get it translated and to follow its instructions. Because its contents hold the key to healing and empowering Earth and humanity, vested interests will stop at nothing to prevent the information from being revealed, and the lives of all three are endangered as their endeavours to protect and act on this information take them across the world, and to a final denouement in Machu Picchu, Peru. Diana Cooper weaves into her story profound elements of spiritual learning, as her characters reveal the seven Great Mysteries that are the spiritual laws of this planet, the illusions by which humans live, the symbols and sounds for unblocking interdimensional portals and the true purpose of Stonehenge and Machu Picchu.