An Altair 8800 kit with 256 bytes of static RAM which I mail ordered from Southwest Technical Products very soon after the January 1975 issue of Popular Electronics. I soldered every component of every PC board, plus all the 100 pin sockets on the backplane the multiple 100 wire connections between the backplane sections. I replaced almost every IC socket with Augat gold-plated machined-contact teflon-based sockets for reliability.
It had a 2 MHz 8080 CPU.
To boot it, every time after turning it on, you had to manually toggle in several dozen bytes of machine code by flipping 16 front panel toggle switches repeatedly to enter the binary codes. Then you cued up cassette BASIC and at the right moment started the cassette recorder.
I gradually added pieces over the next several years, including a couple of colossal 4K dynamic RAM boards, picked up a Model 15 5-level baudot coded newsroom teletype from Atlantic Surplus Sales in Brooklyn, and home-brewed a 60 mA current loop interface. I eventually wrangled a 300 cps optical paper tape reader through a consulting contract in return for developing a driver for it.