Minkowski was the first to reformulate the Lorentz Transformation as a rotation in the spacetime co-ordinate system
(x1, x2, x3, x4), where
x1 = x, x2 = y, x3 = z, x4 = ict
(with c = speed of light, i2 = -1).
A detailed description of this reformulation is available in pdf-format: minkowski.pdf.
It is readable using the freely available Acrobat Reader from Adobe. It was
created using MikTeX.
The figures in this document are repeated below.
Figure 1: Rotated co-ordinate system
Figure 2: Moving co-ordinate systems