My grandfather's ledger book.
He was an engineer and surveyor and, right after the war, he got some lots in trade for delinquent bills from a developer, on one of which he built his home.
He was just starting his business and, every Friday when he knew how much money he had for the week, he would pay all of his bills and buy whatever he could afford that week - a load of bricks, wood, nails, etc. Then, my great, grandfather and he would build as much as they could the following week. It took them a year and a half, but they built the house by hand themselves without ever having any debt.
After he died, my wife and I were in his attic and she found the ledger where he wrote down the initial trade of the land and every single purchase.
I still laugh every time that I look at it.
