Stephen Houston (Brown University)
For the ever-sunny George Stuart, on his birthday
Humans have long been intrigued by the sun, its shadows, and the ways of monitoring them over time. The reasons for that interest are obvious: by paying attention to the effects of the sun, observers could tell the time of day, determine the seasons, and separate or mark parts of the year. But how does one do such tasks precisely? In antiquity, this was mostly made possible by that “simplest” of “scientific instrument[s],” the gnomon (Isler 1991:155). Often little more than a vertical stick or pole, the gnomon cast little shadow at midday. But when the sun rose or fell, shadows extended considerably, and, if observed at equinoxes, aligned with reasonable accuracy to “true” east and west (Isler 1991:180; see also Dash 2017). In China, gnomons (gui biao) showed another innovation. Holes in them would be used to project shadows onto horizontal scales laid out north-south in relation to the vertical gnomon (Li and Sun 2009:1380, fig. 2).
A sundial focuses on the direction of shadows to establish the time of day. More elaborate gnomons target the length of shadows, for this allows the time of year to be determined. In some cases, as in imperial China and early India, measurements of shadows were tabulated over centuries (Yano 1986:26), and the instruments to measure them could be large or even monumental. At Denfeng in Henan province, China, the horizontal scale ran over over 31 m (Li and Sun 2009:fig. 2). Places to observe the positions of the sun have been proposed for much of Mesoamerica, including: caves with overhead openings to permit the entry of sunlight; the celebrated “E-groups,” in part with solar orientations, that coalesced in the Preclassic period; buildings oriented towards sunrise events; and solstitial alignments in doorways at Yaxchilan, Mexico (e.g., Anderson 1981; Aylesworth 2015:787–789; Espinasa-Pereña and Diamant 2012:table 2; Zaro and Lohse 2005:89–93; Tate 1992:94–96). These involved observations, but whether they were “observatories” per se depends on whether a particular feature is “performative rather than practical, a theater rather than a laboratory, a planetarium rather than an observatory” (Aveni 2003:163). In other words, they might have borne witness to solar events, those almost miraculous synchronizations of light, shadow, and place. But they were not “scientific” instruments collecting data over time.
The focus on the sun and its diurnal passage may elucidate an unusual stela erected at the city of Machaquila, Guatemala. Dating to Dec. 2, A.D. 711 (Julian), this monument is, on its front and back, an almost square carving with a head protruding from its top (Figure 1, Graham 1967:87–88, figs. 33). At the bottom is a witz or “hill” element, an emblem of fixity. Just above floats the local king as the embodiment of lordly time at the close of a katun (20-year) period. The glyphs frame that day sign portrait of the ruler with a relatively unembellished, angular sky band that once contained glyphs, now in a poor state of preservation. (Many stylized sky bands take this shape, suggesting a rather rectilinear view of that part of the cosmos.) As for the head, it shows many characteristics of the Classic Maya Sun God: the large “eagle eyes,” possibly crossed (pupils closer to the nose), and a polished mirror-like element in the forehead. Notably, this is the first datable monument at Machaquila, and Andrés Ciudad Real and colleagues have wondered if this carving came just after the movement of the Machaquila dynasty from another location on the Pasión river to the southwest (Ciudad Ruiz et al. 2013:77). The ruler of this time was one Sihyaj K’in Chahk, or Chahk [being] Born from the Sun, a fact inferred from a statement of parentage on the all-glyphic Stela 11 at Machaquila (Graham 1967:fig. 63). Stela 11 dates 30 years after Stela 13, and the reference to this individual by a sequent ruler fits the chronology. That this ruler was “born” from an entity highlighted on the carving is unlikely to be a coincidence. Stela 11 faces west, so viewers would see the Sun God rising from the east, framed above the sky and the floating image, doubtless a portrait, of the current ruler. Much like Chahk, his namesake, the king grasps an axe. He evidently hovered above or was about to land on the firmament of Machaquila itself.
A superb visualization by Andrés Ciudad Ruiz and colleagues reveals the setting of Stela 13 (Figure 2). To the west is a sunken quatrefoil, found on excavation to contain incensario fragments, whistles, and other ceremonial artifacts (Cuidad Ruiz et al. 2010:133–141). As Stuart and Houston noted long ago, this quatrefoil matches the place name of Machaquila (Stuart and Houston 1994:33, fig. 37). On another carving, Stela 10, Chahk looks up from that quatrefoil, in the face-up position assumed by newborns (Graham 1967:fig. 60). This could be another allusion to the first-known ruler at the city, a figure whose very name refers to birth (sihyaj). We do not know for certain, but the quatrefoil could have been basin that filled with water; after all, its excavators note that it was probably plastered at one time, an effective means of keeping water in place (Ciudad Ruiz et al. 2010:133). Behind Stela 13 is an arrangement of two buildings, Structures 17 and 16, numbered from north to south. The cleft between them aligns closely with the top of Stela 13.
This is where the Sun God’s head comes into play. It was not just a deity above a sky band but possibly a gnonom, in the narrow sense of a vertical device used to cast shadows. The sun would rise between the buildings behind the stela, and the shadow of the head thereby reach to quatrefoil in the plaza. For its part, the head would be surrounded by an aureole of light in the early morning. In a straight line from there to the other side of the plaza was a stone model of a cosmic turtle: Altar 4, a conventional representation of the terrestrial world (Graham 1967:92–95, figs. 71–74). The carvings and plaza must have been planned with this alignment in mind. As a sequence of carvings and hollows, Plaza A at Machaquila enchained the sun, time, water, and the earth’s rocky surface (Figure 3).
The shape of Stela 13 has parallels in other sites that are relatively close by. Stela with such everted “tangs” are also documented at the related site of Cancuen, Guatemala, where the Machaquila Emblem is attested in joint use with another, more local title. That second Emblem might have first been used at Tres Islas, a small settlement between the two, larger communities of Machaquila and Cancuen. It was also a place evincing close attention to solar alignments. The three Early Classic stelae at Tres Islas clearly form a single composite image of a central figure over a cave with an ancestral female (Stela 2), flanked by two figures in the dress of Teotihuacan warriors (Stelae 1 and 3); the layout in turn evokes the composition and content of the front and sides of Tikal Stela 31, with the main difference being the separation at Tres Islas of one overall image into three separate carvings. More to the point, the stelae at Tres Islas have been credibly tied to solar alignments (Barrios and Quintanilla 2008: 215–217; Tomasic et al. 2005:392–396). A viewing point from an altar just to the west would look east to the stelae. Behind them, the sun would rise at “true” east for the central stelae, at the equinoxes (or quarter year) for the other two.
At Cancuen, the tanged sculptures include Stelae 1 and 2 (both carved), and Stelae 5 and 8 (both “plain” or unadorned, Tourtellot et al. 1978:227–231). In all cases, these carvings were oriented with one side to the east, another to the west (Maler 1908:fig. 8; Morley 1937:pl. 196b; but note that Gair Tourtellot and colleagues [1978:fig. 5] situated Stela 1 facing south, a fact countered by earlier sources reporting on the site before its carvings were disturbed or moved). Much like Machaquila Stela 13, the tangs on the carvings could also serve as gnomons on an east-west orientation. Indeed, according to Sylvanus Morley, who visited Cancuen in 1915, Stelae 1 and 2 were placed in an east-west line with respect to each others (Morley 2021:230). Stela 1 has another relevant feature (Figure 4). The east side depicts a local queen, the west a later ruler of Cancuen (Maler 1908:pl. 13). Yet the stela also has two quite distinct holes made with obvious care by the sculptor(s); he (or they) visually accommodated the holes by surrounding them with smoky volutes. In addition, there were smaller holes along the side, prompting Maler to speculate that “victims were bound …to these stelae, the sacrifice probably being usually performed with the victim in an upright position” (Maler 1908:44). Such perishable attachments are known in imagery and on Stela 1 from Ixkun, Guatemala (Houston 2016; Stuart 2014), but the main holes hint at conduits for sunlight, in ways that recall the deliberate, calibrated perforations of Chinese gnomons. In China these were arranged north-south, so the parallel cannot be exact. Yet the orientation at Cancuen suggests at least some solar motivation for the holes. At dawn or sunset light would pass through, to shine on some surface in front or behind the stelae, and perhaps on each other.
The suggestion that the Sun God head at Machaquila, the “tangs” at Cancuen, or the perforations on Stela 1 at that site operated as gnomons for light and shadow accords with their position, orientation, and imagery, especially at Machaquila. If gnomons, they could have been performative, even providing a kind of cosmic theater, but the play of light perhaps helped with observations too. A careful study of them is impeded by looting and displacement of carvings; many monuments are no longer in their original position. Nonetheless, it seems possible that, at sites far beyond Machaquila and Cancuen, the Maya choreographed and manipulated beams and shadows from the sun. Stelae were freestanding, yet, by such displays, in ways not yet fully studied or understood, they interacted with spaces and surfaces nearby.
 In a recent email, Walter Witschey, a Mayanist colleague, informs me that, for a time, he held the record for the largest analemmatic (graduated scale) sundial ever made: “for size (1/3 acre)[,] gnomon height (25′)[,] and accuracy (30 sec midday and 5 sec early morning and late afternoon).” Clearly, this is not an exhausted skill or art form. After this was first posted, Kristin Landau also drew my attention to an intriguing paper on Copan Stela D as a possible gnomon (Pineda de Carías et al. 2017).
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