Is it possible to write a transaction of bitcoins, having only pen, paper and a private key from the address with some unspent outputs? In my last answer I have done an allegation which I want to be proven or disproven. If this work possible, how much paper does it require? What kind of software needs Bob to send a transaction to miners?
The transaction digest alone would take around 2 days of non-stop work:

http://www.righto.com/2014/09/mining-bitcoin-with-pencil-and-paper.html

That's before you even start the 32-byte multiplication required to compute an ECDSA signature.

It might be humanly possible if the UTXO you are spending does not require a signature. An "anyone-can-spend" transaction would only take a few minutes to assemble since they require no input script. But then of course anyone could steal your coins before your TX got confirmed.