Mrs. Beeton published this pattern in her 1870 book Mrs. Beeton’s Guide to Embroidery, Crocheting and Knitting. Her pattern was knit in the round. I prefer Weldon’s knit-flat version from 1888 Weldon’s Practical Needlework, vol. 1, p.5. I made slight changes to correct errors and to match Weldon’s engraving better.
This pattern is quicker and easier to work than it looks! There are only 44 rows and half of them are “purl across”. The pattern is visually easy to follow and is symmetrical about the center stitch.
A 4-triangle block is 6” square at gauge.

Skills needed: cast on, slip, knit, purl, YO, SSK, k2tog, SK2P (double decrease) and bind off in knit or stretchy stitch.

Gauge is not important in this pattern. Any block-able yarn/thread will work. Make a swatch to check gauge and appearance.

24 yards of #10 crochet thread will make a triangle in the stated gauge.
100 yards will make a 4-triangle square.