Last week's episode of "Patented" discussed the use of sink for escape maps given to British soldiers in WWII. Check out the detail of those maps! https://macc

Last week's episode of "Patented" discussed the use of sink for escape maps given to British soldiers in WWII. Check out the detail of those maps! https://macclesfieldmuseums.co.uk/wwii-silk-escape-maps https://macclesfieldmuseums.co.uk/wwii-silk-escape-maps And of course this HN post needs a reference to Neal Stephenson's "The Confusion" (The Baroque Cycle, Vol. 2) where Eliza codes her letters into her knitting.