Sitting in the lotus position, the mummy fits within the statue perfectly.
"On the outside, it looks like a large statue of Buddha," the museum said in a release. "Scan research has shown that on the inside, it is the mummy of a Buddhist monk who lived around the year 1100."
Glowing through the statue's golden cast, the human skeleton is believed to belong to Buddhist master Liu Quan, a member of the Chinese Meditation School.
To further investigate the mummy, the researchers took the statue to the Meander Medical Center in Amersfoort and carried out an endoscopy and additional CT scans.
They found out that Liu Quan's internal organs had been removed and replaced with scripts covered in Chinese writing.
The museum speculates Liu Quan may have "self-mummified" in order to become a "living Buddha."
Practiced mainly in Japan, self-mummification was a grueling process that required a monk to follow a strict 1,000-day diet of nuts and seeds in order to strip the body of fat. A diet of bark and roots would follow for another 1,000 days.
At the end of this period, the monk began drinking a poisonous tea made from the sap of the Japanese varnish tree, normally used to lacquer bowls and plates. The tea caused profuse vomiting as well as a rapid loss of bodily fluids, possibly making the body too poisonous to be eaten by bacteria and insects.
A living skeleton, the monk was then placed in a stone tomb barely larger than his body, which was equipped with an air tube and a bell.
Never moving from the lotus position, the monk would ring the bell each day to let those outside know that he was still alive. When the bell stopped ringing, the monk was presumed dead, the air tube removed and the tomb sealed.
After another 1,000 days the tomb would be opened to check whether the monk had been successfully mummified. Of the hundreds of monks that tried this horrifying process, only a few dozen actually became self-mummified and venerated in temples as a Buddha.
Researchers aren't certain when or how this monk's organs were then removed and replaced with scripts.
The Buddha statue is currently on display at the National Museum of Natural History in Budapest. It will remain there until May.
Image: A scan reveals the body of a nearly 1,000-year-old Buddhist monk inside the statue of Buddha. Photo by M. Elsevier Stokmans; Boeddhamummie (Drents Museum)Drents Museum.