A nice little article about hardtack

http://militaryhistorynow.com/2014/07/11/hard-to-swallow-a-brief-history-of-hardtack-and-ships-biscuit-2/
I finally purchased ant tried some hardtack last year.  Have always wanted to see what it was like.  My experience was that it looked like a giant saltine cracker, and tasted like that, too - but without any salt.  With about four times the thickness - and VERY dense.  It wasn't something I feel the need to eat again, but was not as awful as some descriptions that I've read.  I found that soaking it in a bowl of chili for a minute or so worked pretty well.