A spot is selected to mark out a templum on the ground, drawing out first the cardo running east and west, then the decumanus running north and south, according to astronomical observations. The same is described for laying out an estate, as Pliny mentions (NH XVIII.76-77), or a military camp, a colony or a city. The cardo is determined by the point on the horizon where the sun rises and sets, altering through the seasons, and not by determining the true east-west direction. The decumanus is determined by observing Polaris and not by employing a compass. Then two sets of parallel lines are drawn to form a rectangle in a proportion of 6:5. At the center of the templum the Romans would erect a tabernaculum, a square tent with its opening facing south.
The magistrate taking the auspices is referred to as an auspex, distinct from the augurs who interpret the signs (Cicero: On Divination 1.48; On the Nature of the Gods II.3; On the Laws II.13). The auspex sits out in front of the tabernaculum, usually near the edge of a hilltop, while his assistants and the tibicines and tibicinae will stand within. The purpose of the tabernaculum was to avoid the auspex from being distracted by auspicia oblativa, or naturally occurring omens, and that he might concentrate on the auspicia imperitiva being sought in the sky (see below).
Throughout the ceremony the tibicines and tibicinae are to play their flutes. Mention is made in the ancient texts that this was done to prevent the magistrate from being interrupted by the sounds of any ill omens. However there may have been more to this and the flute players might have also been present to draw birds to the templum. It was normal practice to have tibicnes and tibicinae play during any Roman ceremony, as a way of pleasing the gods. The first step in the ceremony would be to perform a libation to Jupiter, stating the reason that auspices are being taken and asking that He give his approval. Only Jupiter sends the birds to act as messengers of the gods in public auguries (Cicero: On Divination 2.34, Aves internuntiae Jovis; On the Laws II.8, Interpretes Jovis optimi maximi publici augures). For private auguries other gods or goddesses may be called upon and a sacrifice would then be offered to them. One emblem of an augur is the special earthen vessel (capis) used in making this libation. Incense and flute music are also offered as a part of this opening sacrifice.
Next the magistrate would employ his lituus to designate another templum in the sky. A lituus is a special wand of augury, made from a tree branch (possibly ash or hazel) without any knots and with one end naturally curled. With the lituus he would again draw out a templum by designating the cardo and decumanus. One formula has the auspex call out, “This shall be to my left is the East, and this to my right shall be the West. This before me is South, that behind me is North.” Then the enclosing sides are drawn. The boundaries of this celestial templum are designated by the auspex in calling out points of reference on the ground. Varro says that different formulas were used to designate a templum, and offers one such formula as was used on the Arx:
“Let the boundaries of my templa and the wild lands (tesca) be as I declare them with my words. That tree of whatever kind it is which I deem myself to have named, let it be the boundary of my templum and the wild land to the right. That tree, of whatever kind it is, insofar as I deem myself to have named it, let it be the boundary of my temple and the wild land on the left. Between these points I have established the templa and the wild lands by means of directing (conregione), viewing (conspicione), reflecting (cortumiones) as far as I have been most rightly aware of it within this limit.”
(Varro: On the Latin Language, VII.8)
The plural form is used here, seemingly making each boundary line a templum. Varro goes on by quoting from Ennius’ play Medea, “Contemplate and see the templum of Ceres on the left…” to draw a parallel between the words contemplate (contempla) and templa. The formula also mentions the plural form tesca that is translated as “wild lands” but these are rural sanctuaries of gods. The area within the boundaries of the rectangular templum is divided into four quarters by the cardo and decumanus, and there were further divisions, to a total of sixteen, each division dedicated to a particular divinity. A similar practice is found in the Etruscan practice of haruspicy where the liver of a sacrificial animal is divided into sixteen sections, each associated with a particular divinity. This formula by Varro seems to indicate that other regions beyond the designated templum were also associated with divinities. The cardinal directions marked out above were associated with light and life in the East, darkness and death in the West, the abode of the gods was held to be in the North, while the South was associated with the lower regions of the earth and below.
Once the templum is established, the auspex would then pray, “Juppiter Optimus Maximus, and all You other gods and spirits whom it is proper to invoke, I ask that if it is good and right that (the proposed action) be done, that You will send clear and certain signs within the boundaries that I have marked.” Here the auspex may specify the kinds of signs he wishes to appear within the templum he has marked out. These become the auspicia impeeritiva that he must watch for. He may also designate other signs that he will ignore, whether within or outside the templum. These, together with all other omens, become auspicia oblativa, and while they may be noted and used in clarifying more details about the augury, they are not to be considered as omens specifically answering the question posed. The auspex then awaits the auspices by watching the sky (sevare de caelo) for signs (spectio). This was to be done without interruption (silentium; silentio surgere) and anything that might make the augury invalid was called a vitium. For the auspices taken for inaugurating an official, the templum that was drawn and established on the ground might be made after midnight, where the auspex would remain in contemplation and offering sacrifices to the gods. Just before dawn he would then draw the templum in the sky and begin to look for signs.