Culet

The Turk prosecuted his advantage to the uttermost of his power; yet the other[…]not onely avoided the Turkes violence, but having drawne his Faulchion, pierced the Turke so under the Culets thorow backe and body, that although he alighted from his horse, he stood not long ere hee lost his head, as the rest had done.

1999, John W. Kenney, III, 7. Pressure Effects on Emissive Materials, D. Max Roundhill, John P. Fackler Jr. (editors), Optoelectronic Properties of Inorganic Compounds, Plenum Press, page 234, The common diamond cut for high pressure work is the modified brilliant cut (see Fig. 1) in which the point of a brilliant cut diamond (i.e., the type of diamond commonly found in an engagement ring) is lopped off to provide a flat surface, called a culet, for pressure transmission. Two opposed diamond culets, separated by a thin, extrudable metal gasket into which a small sample hole is drilled, are squeezed together mechanically to reduce the volume of a hydrostatic medium and thereby increase the pressure of the sample as shown in Fig. 1.

2006, Antoinette Leonard Matlins, Diamonds: The Antoinette Matlins Buying Guide, LongHill Partners (GemStone Press), 2nd Edition, page 85, The culet looks like a point at the bottom of the stone, but it is normally another facet—a tiny, flat, polished surface. This facet should be small or very small. A small or very small culet won't be noticeable from the top. Some diamonds today are actually pointed. This means that there really is no culet, that the stone has been cut straight down to a point instead. The larger the culet, the more visible it will be from the top. The more visible, the lower the cost of the stone. Stones described as having a large or "open" culet, such as old-European or old-mine cut diamonds (see chapter 5), are less desirable because the appearance of the culet causes a reduction in sparkle or brilliance at the very center of the stone. For the same reasons, a broken or chipped culet will seriously detract from the stone's beauty and significantly reduce the cost.

2012, Samuel T. Weir, Yogesh K. Vohra, Chapter 4: Advances in Customized Diamond Anvils, John Loveday, High-Pressure Physics, Taylor & Francis (CRC Press), page 68, A final step is to polish the rough as-grown diamond layer on [the] culet of the designer anvil to smooth the surface and shape the culet so that is suitable for high-pressure experiments.