Bone carving is one of the oldest art forms. Back in ancient times, people used animal bones not only for needles, arrowheads, combs, scrapers and other necessary in everyday objects, but also for sacred items and jewellery. As the years went by, the interest in bone products did not die out, but on the contrary -- it increased, gradually moving from the field of domestic use to the field of applied art.

In Asia and the East, special schools were formed where the subtleties of artistic bone carving were passed on from generation to generation. In China, it is one of the oldest and most revered forms of art. This art reached its greatest heyday during the Ming Dynasty (1368-1644), when Chinese sculpture acquired a pronounced decorative character.  The most famous works of Chinese masters are considered to be "balls in a ball" or "devil's balls "*.
The history of this unique craft of creating puzzle balls with inner spheres that rotate freely within each other goes back about 1000 years.

The art of bone started developing in the Celestial Empire as early as the 3^rd -10^th centuries. This craft reached the peak of its popularity during the Ming dynasty. It was at this time that various trinkets and household items began to be carved from ivory: boxes, trays, picture frames, smoking pipes, snuff bottles, cages for birds and crickets and the like. As the mastery of craft developed, two main schools of ivory carving emerged in China: Beijing and Canton (Guangzhou).

The Beijing school was characterised by laconic forms and restrained decoration. The masters here mainly created human figures, often colouring the bone with bright dyes to make the pieces more decorative. The masters of the Canton school, on the other hand, focused on more complex carvings. But initially their mysterious balls were very primitive. Their production turned into a high art when steel carving tools were brought from Europe to China, which allowed them to skilfully display even the smallest details in their products.

And for many centuries the creations of masters of this school are amazing mankind with their unearthly beauty and unique technique of execution. To this day in China the centre for the production of multilayer openwork spheres is considered to be the city of Guangzhou, formerly known as Canton.

The oldest such sphere, consisting of only three layers, dates back to the Song Dynasty (960-1279). The first documentary mention of carved puzzle balls can be found in the book by Cao Zhao "The Basic Criteria of Antiquity", dating back to 1388.

It is not surprising that everyone who sees this miracle for the first time tries to understand, at least theoretically, the sequence of actions of the master creating the mysterious ball. And if we take into account that they were made in ancient times, when there were neither modern milling machines with numerical control, nor even conventional steel tools, it is difficult to imagine how it was possible to create such miracle balls ....

Each such ball is carved from the same piece of material as all previous ones; it is one piece, not collapsible. This is why ball-in-ball carving involves incredibly delicate and painstaking work. If a carver in the Middle Ages took up work on such a ball -- it meant that the artisan would work on this object all his life. And the more richly he decorated the external ball and the more inner balls -- the more expensive his product was valued.
So, first, the master gives the elephant tusk fragment the shape of an ideal sphere, and then he cuts several cone-shaped holes in it, the tops of which should converge in the centre of the sphere. Then he makes marks in each hole, thus determining how many spheres will be inside the largest sphere. The work begins with the central ball, which is cut from the inside, and then alternately all the subsequent ones -- towards the external layer. For this purpose, a special curved L-shaped cutter is used, which is driven inside the ball through one of the cut holes and separates one ball from the other. And then, the resulting balls, moving one in another, are covered with fine carving or engraving by the master one by one, while rotating them in each other.

The top ball is much thicker than the others, and the master decorates it particularly carefully. Usually dragons, a phoenix bird or flowers are carved here. By the way, all these symbols, according to Chinese mythology, carry positive energy and are aimed at preserving and strengthening health and well-being.

It goes without saying that the craftsman who performs this fine jewellery work has to rely only on his own intuition, years of experience, the sharp blade of his cutter and his hand steadiness. After all, the made holes do not allow him to see everything that happens inside the ball. And if the master makes a mistake even half a millimetre, his work will be meaningless.

Nowadays, this unique form of arts and crafts is still very popular in China. In the 20^th century, carvers specialising in the production of such balls reached an incredible level of skill. While the very first "puzzle balls" consisted of only three layers, gradually over the centuries skilful carvers managed to increase their number to seven. In 1915, a Chinese carver amazed visitors to the Panama International Fair with a bone-carved ball containing 25 openwork balls inside. In 1977, his son, Weng Rongbiao, broke the record by producing a marvellous ball, inside which 42 patterned balls were free to rotate, each one moving inside the other and decorated with engraved landscapes of pavilions and towers, clouds and mountains. Its diameter was 15 centimetres, while the smallest inner ball was no more than the thickness of a sheet of paper. 

Such masterpiece was first created about thousand years ago. Customers in the West were amazed by the superior quality of carved works made in the Celestial Empire. Bone carving in China is now recognised as a national heritage. This art is still popular despite the ban on the ivory trade.

The section of the museum collection "Lapidary and Bone-carving Art" features a similar puzzle ball made by Chinese artisans in the 20^th century. The ball is made of ivory and consists of 15 layers, which can be combined so that all the holes coincide. The top layer is decorated with an exquisite carved floral pattern with thoroughly detailed carved roses; the inner layers are decorated with reticulated floral pattern. The ball is placed on ivory base with the stem decorated with a smaller puzzle ball, with the top layer in the form of an intricately twisted Chinese dragon; the round base is decorated with carved floral pattern similar to the one that ornaments the top ball. The height of the object is 22.8 cm.

Ref.: https://kulturologia.ru/blogs/180721/50451/
https://bonecarving.ru/istoriya-zarozhdeniya-rezbyi-po-kosti.html
https://dzen.ru/a/YFgyB4MiTFf7Z16H
https://koptelovy.ru/item/rezba-po-kosti-odin-iz-vidov-dekorativno-prikladnogo-iskusstva/