Today's prompt, "Written Source," was tricky for me until I remembered my favorite trio of indispensable little books:
These handy little manuals have all manner of techniques and tutorials, and with a period binding you can take them anywhere with you. I don't pull them out for every project, but when I need them I just can't do without! You can get them directly from the authors at Kanniks Korner, from Burnley & Trowbridge, Wm. Booth Draper, and even Amazon. They're also ebooks, although obviously those aren't historically accurate!