Patolli

Cut a 60 x 60 cm square of cotton cloth, woven mat or leather. Boards were painted on cloth, matting or hide; the ones nobles owned were wooden tables with inlay.

Mark the centre and draw two perpendicular lines right across the cloth. The four arms of the cross are built on them.

Draw each arm as two parallel rows of squares running out from the centre. The finished figure is an X or saltire, not an upright cross.

Divide the arms until they total 52 squares, shared equally between the four. That number is the 52-year cycle and should not be adjusted to make the drawing easier.

Shade the squares at the tip of each arm and the two central ones on each. In the reconstructions these cost a turn or grant another throw.

Go over the lines with paint and let it dry thoroughly. Boards usually carried good-fortune symbols around the playing area as well.

Take five large beans and put a white mark on one face of each — a scraped patch or a dot of paint. Each bean is a two-sided die: marked or plain.

Prepare six pieces per player, a different colour each. Maize kernels, stone discs or carved shells all served, depending on what was to hand.

Agree before starting where each player enters and which way round the board they travel. It is a race: first to bring all their pieces home wins.

Throw the five beans and count how many land marked-side up: that is how many squares you move. If none land marked, the turn is lost.

If a piece lands on a square held by an opponent, that opponent's piece leaves the board and starts again. This is what turns a game of chance into a game with decisions in it.

A piece that completes the full circuit leaves the board and is safe. The first player to retire all of theirs wins.

Write down the results of twenty throws and compare them with expectation: with five fair beans the commonest result is two or three marks. It is a good probability exercise using fifteenth-century equipment.

A Mesoamerican race game. Patolli was played in central Mexico before the conquest and belongs to the race-game family: pieces travel a circuit as chance dictates, with captures along the way. It has been compared to pachisi from India, and that resemblance fed an old diffusion argument that is better explained today by convergence — the race board is an idea that gets invented independently in many places.

The board is a calendar. The 52 squares correspond to the Calendar Round: the 260-day ritual calendar and the 365-day solar year come back into alignment every 52 years. To play was to travel that cycle.

The stakes were serious. The chronicles describe wagers of cloaks, jewellery and, in extreme cases, a player's own freedom. The game was associated with Macuilxochitl, a deity of games and dance, and carried a divinatory character — the outcome was read as a sign. That is set down here as history; the blueprint teaches how to build and play the board, not how to gamble.

What we do not know. The Spanish banned the game and burned boards; what survives are descriptions written by chroniclers such as Sahagún and Durán, plus a few depictions in the codices. Edward Burnett Tylor reconstructed the basic rules from those sources in the nineteenth century. So any modern rule set — this blueprint's included — is a reasoned reconstruction, not the game as it was played. Saying so matters: presenting a reconstruction as the original is exactly the kind of error that gets inherited for centuries.