We all know the things we can’t do on Tisha B’Av. But just not doing stuff can’t be the whole story. The real point, I suppose, is the mourning. But how does that happen?
The poskim (אורח חיים תקנ”ד) point to a custom to avoid labor (מלאכה) and business (בפרקמטיה). That, no doubt, is to keep us from being distracted from the mourning. We’re also expected to refrain from learning most Torah sources as it’s assumed those will give us joy.
The tefilos and kinnos are certainly there to help us focus on this specific flavor of mourning. But tefilos don’t take that much time, and the kinnos - even when properly understood - are relatively modern: it’s unlikely that any of them is older than 1,000 years, and it’s only very recently that we began reciting the “whole book” regardless of our individual family traditions. So how did our ancestors from previous centuries actually fill the day?



