Harold stood in the doorway to the Arithmancy classroom, and quietly shook his head. "Oh, dear, this will not do at all. Or rather, it will do, once everything is ready."
The Arithmancy classroom is superficially no different to any other classroom in Hogwarts. It has the general rectangular shape of other classrooms, but unlike other of the classrooms that divide the room into rows and all face the lecturer in unison and uniformity, the Arithmancy classroom is arranged into clusters, or perhaps better described as 'pods'. Tables for a handful of students to work together in small groups.
The doorway opens on one of the narrower sides of the rectangle, and leads to a very large chalkboard, and a large table before it, which appears to be on a slightly raised dais. It is clear, then, that the chalkboard - which, must be said, covers a large percentage of the wall - is the prime focus of the room, even with the clusters of seating arranged around it.
The other long wall has two large windows in it, in the classical medieval style, and sat between them in a cupboard. The cupboard is bolted shut with three very large, very heavy looking deadbolts. There is a small handwritten note on it which indicates that, currently, it has four copies of Numerology and Grammatica, two copies of Encyclopedia Numerologica and some notes on various equipment currently stored away. All of which was noted in a very precise, tidy handwriting.
There are some spare stacks of parchment and bottles of ink on the table before the room.
On the chalkboard, in the same precise handwriting as the note on the cupboard, is a series of three statements, underlined.
He who can observe, can measure
He who can measure, can understand
He who can understand, can manipulate
He who can master these disciplines,
is master of all that is magical