A short essay by Ralph Griswold using satin counters as an example of how weaving books explain mathematical topics. It quotes five authors' descriptions of how to choose a satin counter, points out their incompleteness or unclear wording, and restates the rule in mathematical terms (relatively prime i and j with i + j = n). It ends with a table of the smaller satin counters for 2 to 24 shafts and a note on prime shaft numbers.