The elements of the alchemists were mercury, sulfer, and salt, and supposedly they could turn lead into gold with some combination of these elements. It has been proven that spontaneous generation of neutrons is possible (the discovery of cold fusion, 1989), so it is likely that the alchemists could indeed turn lead into gold.
Given the large number of available substances which were elements and those that could pass for elements (such as gemstones: diamond, emeralds, etc...), it defies all mathematical and statistical probablity that the alchemists could have stumbled upon the two correct elements (mercury and lead) by pure chance. It would be similar to a chimpanzee choosing these two elements out of the total 92 known natural elements by random chance.
Also, far more gold was found in South American pyramids and their associated structures and temples than could be explained by the number of gold mines and the level of mining technology of the time. Many theorize that the pyramids in Egypt were built by aliens. The great pyramid does not vary from pure geometric perfection by more than 1/4 inch over its entire overall dimension, an engineering feat which until 10 years ago, modern man did not possess the technology to duplicate. It takes laser cutting and alignment tools, and supercomputers to calculate the block deformation values for the individual blocks. (each block compresses and deforms from the weight of the blocks above).
About the time that Atlantis was said to have been destroyed, about 4000 years ago, pyramid construction began in South America. Although these pyramids were far inferior in design and scale than the ones in Egypt, the timing is not coincidental. The few Atlanteans who survived trying to save what was left of their culture?
A picture of an airplane was found carved into the wall of a South American cave. Radiocarbon-14 dated it to 4000 years ago. They found a gourd that had been fashoined to serve as a battery, with a zinc and a copper electrode: pour grape juice in, and it produces electricity. This item was radiocarbon dated to 4000 years ago.
But the most obvious evidence is the alchemists. The alchemists obviously knew the existence and composition of the periodic table of elements.
The facts point to a very advanced level of scientific understanding and knowledge that was wiped out of existence some way or another, about 4000 years ago. Modern man did not begin rediscovery of the table of elements until about 600 years ago. In the interim, man beleived there were only 4 elements, earth, water, fire, and air.
Surely one of the last Atlantean communications satellites fell and partially burned up in the atmosphere in the 1950s, and the Air Force wonders to this very day why the "aliens'" technology they stored away in Hanger 18 at Area 51 wasn't that much more advanced than our own.
I suggest "Gods and Spacemen in the Ancient East", author unknown. However, I wouldn't be too quick to blindly accept the author's theories. As near as I can tell, most af the author's theories are totally mistaken. However, the book is a priceless historical reference, and contains excerpts from the Egyptian Book of the Dead, the Hindu Ramayana, and other ancient texts. The book suggests that there have been at least four great civilizations on the earth before this one, Atlantis only being the most recent one before us.