https://www.w3.org/TR/css-multicol-1/

The i18n WG was glad to see that the spec mentions that column directions are logical and will look different in vertically set text. Thank you. However, the text describing that could be missed if you blink, and therefore we would like to suggest the addition of a note which gives examples of columns in both Japanese and Mongolian, just to ensure that implementers (and content authors) have a clear picture of how this should work.

The note should probably introduce the idea that columns run horizontally in vertically-set text, and explain that the block flow direction can vary. It may also be an opportunity to remind readers that 'width' refers to the length of the text line, rather than the physical horizontal width of the column.

There should probably also be tests for vertically set text (maybe there already are?).

Here are a couple of images you could use as illustrations. It might be good to add arrows indicating the reading direction, but we supply the images raw for now.

Japanese (columns read RTL):

Mongolian (columns read LTR):