Siamese cat including the Cornish Rex, Sphynx, Peterbald, and the blue point Siamese cat. The Siamese cat comes in two distinct variations: traditional, with an apple-shaped head and a slightly chubby body; or the modern Siamese, which are very skinny and have a wedge-shaped head. Both a description and depiction of the Wichienmaat (Siamese cat) first appears in a collection of ancient manuscripts called the Tamra Maew (The Cat-Book Poems) thought to originate from the Ayutthaya Kingdom (1351 to 1767 AD). Over a dozen are now kept in the National Library of Thailand, while others have resurfaced outside of Thailand and are
Crystallographic point group known as a crystal class. There are infinitely many three-dimensional point groups. However, the crystallographic restriction of the infinite families of general point groups results in there being only 32 crystallographic point groups. These 32 point groups are one-and-the same as the 32 types of morphological (external) crystalline symmetries derived in 1830 by Johann Friedrich Christian Hessel from a consideration of observed crystal forms. The point group of a crystal, among other things, determines directional variation of the physical properties that arise from its structure, including optical properties such as whether it is birefringent, or whether it shows the Pockels